Perhaps the greatest scholar of the 19th century Hebrew Christians, Biesenthal was widely known, but I have been unable to find a photograph of him. The account in Bernsteinreads:
Biesenthal, Dr. Joiachim Heinrich—or, to give him his birth-name, Raphael Hirsch—was born at Lobsens, in the Grand Duchy of Posen, on December 24th, 1804, of pious and strict Jewish parents. His early education was chiefly confined to the study of the national law and tradition; and through much self-denial and sacrifice on the part of his parents, who intended him for the rabbinate, he was able to have lessons from the best teachers and most learned Talmudist scholars of the day. He was what is called a Bachur (lit. “young man”), a student of the Beth Hamidrash, who is intended for the study of the law. The Talmudical principle, “Know well what to answer an infidel,” particularly moved his father to insist that he should join with the study of Talmud that of the Holy Scriptures and Jewish poetry. He soon found, however, that as regards his study of the Bible he was left to his own diligence and perseverance, for his teachers knew nothing at all about it; and, being imbued with the Talmudical warning—”Keep your children from the study of Holy Scripture,” they were of opinion that it was not only a useless study and waste of time, but also a danger to one’s piety.
In 1819, when Raphael was fifteen years of age, the town of Lobsens was destroyed by fire, by which his parents were ruined. His education, however, had to be completed, and so he entered the famous Jewish school of Rawitsch, where he received instruction  from rabbis, and principally from Rabbi Herzfeld, of European renown. Deprived of every assistance from home, young Raphael had to struggle hard during his four year’s residence there. On leaving Rawitsch he went to Mainz, where he received most kind care and support from the Rabbi of that city, Löb Ellinger, brother of the renowned Nathan Ellinger, or Nathan Bar Yospa, rabbi of Bingen, several of whose manuscripts are in the Bodleian.
The celebrated Heidenheim (Wolf Ben Samson) of Rödelheim, the greatest Jewish critic and grammarian after Ibn-Ezra and David Kimchi, helped him to the treasures of Jewish literature, lending him the best grammars in the Hebrew language, so that he was able to acquire, with great application on his part, a complete mastery of grammatical Hebrew. He next gave himself up to the study of German history, and Latin and Greek. His studies threw him into contact with the Rev. Dr. Klee, Roman Catholic Professor at Bonn, who gave him lessons in Hebrew, and introduced him to the Duchess of Coburg, the wife of General de Mensdorff, Governor of the fortress of Mainz. From her, and all the family, Raphael received many substantial proofs of kindness, and when he was about to leave Mainz, which he did in 1828, she gave him a considerable sum of money, and a letter written by herself to Baron de Rothschild, of Frankfort-on-the-Main, and graciously intimated that she would be glad to hear how he was getting on in life. Raphael found the Baron not inclined to assist him when he heard that he meant to finish his studies  at Berlin, because he considered that a dangerous city, where all young Jewish students were being converted to Christianity. That there was great truth in this statement will appear lower down. “Keep away from a city where thousands become apostates!” were his parting words. Baron de Rothschild, however, sent him a letter of recommendation to Baron de Hägemann, the Chancellor. When Raphael delivered the letter, the not unnatural remark was, “What is the use of a recommendation for assistance from Rothschild! Why did he not help you himself?” So he was obliged to shift for himself at Berlin, and to earn his living by giving lessons. He employed his leisure time in study. In the year 1830 he resided for four weeks with a Christian family at Havelberg, where he learnt for the first time what true Christianity was, and he determined, as he said, to “search for Christian truth.” In this purpose his intercourse with Christian divines greatly helped him. He studied theology and philology in the University of Berlin from 1828, taking his doctor’s degree in 1835. He studied under the Oriental scholar, William Vatke, and his knowledge of the Hebrew grammar was greatly increased by personal friendly intercourse with Dr. Gesenius, the distinguished Hebrew scholar, at Halle. Raphael was baptized in 1836 by the Rev. Dr. Kuntze, taking the Christian names of Joiachim Heinrich and the surname of Biesenthal.
That there was a considerable truth in Baron de Rothschild’s observation given above, is seen from the statistics of Jewish baptisms in those days. 
Dr. Kuntze, who was a resident clergyman at Berlin, was instrumental in leading many young Jews to Christ. He baptized eighty in eight years (1829-36), whilst the Society’s missionary, the Rev. W. Ayerst, baptized forty-two adult Jews in three years (1834-7). Altogether, 326 Jewish baptisms were registered in the Consistory at Berlin during the years 1830-37. A few years later (1844) the Rev. C. W. H. Pauli, the Society’s missionary, reported that there were above 1,000 converts resident in Berlin; and in 1850, as many as 2,500. They filled all ranks and stations, and were to be found in all the ministerial departments, and in the university.
In 1844, Biesenthal placed his services at the disposal of the Society, and in doing so, wrote: “My Biblical studies led me, after much searching and wandering for a long time, to find Him of whom Moses and the Prophets did write. This result, this light which God caused to shine in my darkness, I deem it my unrelenting duty to communicate to others yet living in darkness, because the Lord Himself says that we should not put our light under a bushel. The Apostles, as well as all the Fathers, were furthered by the same disposition of mind. ‘For where your treasure is, there will your heart be also,’ says the Lord. If Christ be our treasure, our heart must be entirely and undividedly His own, and all our talents devoted to the glory of His kingdom. Becoming a missionary seems to me the surest way to fulfil Christ’s commands. I have long considered it both a duty and a privilege to communicate to my brethren after  the flesh the message of salvation, and to employ those talents which God has given me for their welfare. My predilection for the above has often seemed to be a token of God’s will that I should shew my brethren from their very literature, as well as from the Bible, that the treasures of wisdom and knowledge are hid in Christ, and that we can only know the Father through Him. During the last three years I have acted upon this conviction, and embraced every opportunity to prove to my brethren that the Gospel of Christ is the power of God unto salvation, and my anxious desire now is to be enabled to devote all my time to this pursuit.”
These earnest words are an echo of St. Paul’s, “My heart’s desire and prayer to God for Israel is, that they might be saved” (Rom. x. 1). With this spirit and aim, Biesenthal entered upon his long missionary career of 37 years in connexion with this Society—active laborious years spent in Berlin (1844-1868) and Leipzig (1868-1881). Eloquent in the Scriptures, with a perfect command of Hebrew and wide knowledge of Talmud and rabbinical literature, he was thoroughly furnished for his life’s work. Those who knew him well believed that he had intellectual, literary and biblical qualifications in a most eminent degree, and that he was the best Hebrew scholar of their acquaintance. His knowledge of languages embraced—in addition to his native Polish—Hebrew, Latin, Greek, Syriac, Chaldee, Arabic, Ethiopic, Samaritan, French, German, Spanish, Italian and English. Never was missionary more highly gifted  with “tongues”—his equal in this respect is not to be found in the ranks of the London Jews’ Society; whilst with his pen he did even better service than with his lips in proclaiming “Jesus Christ and Him crucified” to his brethren after the flesh.
Biesenthal’s missionary life commenced on April 1st, 1844, as an assistant missionary in this Society’s mission at Berlin, under the Rev. C. W. H. Pauli, where he also undertook the editorship of “Records of Israel’s State and Prospects,” a monthly periodical designed to promote the Society’s work, to give treatises on Messianic passages of the Old Testament, to discuss Christian and Jewish doctrines, and to give attention to Jewish history and literature; he also wrote many articles for the “Dibre Emeth.” He continued to work in this humble capacity under the Rev. R. Bellson until 1868, when his great abilities found a recognition, even though tardy, by his appointment to the charge of a new mission station of the Society at Leipzig. This important city, the second in Saxony, and the seat of a university, had for many years been visited by the Society’s missionaries from Berlin at the time of the great fairs, when Jews assembled from all parts, and to whom large numbers of Old and New Testaments were sold. Biesenthal found some seventy or eighty Hebrew Christians living there, and subsequently gave it as his opinion that they might be “numbered by hundreds.” There was a small Jewish community of about 500, who, since 1849, had enjoyed the rights of citizenship. This may seem to have been but a small field of work  for a man of such attainments, but he was the only missionary to the Jews throughout the whole kingdom of Saxony; and, moreover, Leipzig was the resort of many foreign Jews from Poland, Russia, Turkey, Greece, Persia, and even from America, and thus altogether an important missionary centre. Apart from the visible results in the form of baptisms from Biesenthal’s labours, the indirect results were great and far-reaching. As a scholar his name was, for many years, a household word in Germany, and especially in those circles where the Jewish mission exerted its influence. His Commentaries on the Gospels and the Epistles to the Romans and the Hebrews, so eminently useful in mission work, obtained well-deserved eminence.
The mission field, as time went on, became less promising and fruitful, the Jews becoming infected with the socialism and rationalism in Germany, as taught in the universities, churches, schools, and other institutions. Zeal for missions almost died out; the Jews became the subject of much Anti-Semitism. The long pent-up enmity against them burst forth with great virulence. In Leipzig, as in other places, petitions were sent to the Government urging the withdrawal of their political rights and privileges. In return, the Jews paid back hatred by hatred.
This state of things led Dr. Biesenthal to take a gloomy view of the general position. In his last report but one he said: “Hurricanes of trouble are blowing from the four quarters of the earth against the Church and against the Gospel,” and added that  in such circumstances his report could not be a joyous one.
Dr. Biesenthal doubtless obtained more satisfaction from his literary than from his missionary labours; although, in his case, one was the complement of the other. A scholar he was emphatically, and a brilliant one withal, as his works abundantly and substantially testify; and as such he will be principally remembered.
His published works contained the following: “Auszüge aus dem Buche Sohar, mit Deutscher Uebersetzung” (1837), a proof from Jewish sources of the doctrine of the Trinity and other Christian verities; “Hebräisches und Chaldäisches Schulwörterbuch über das A.T.” (1836-7); “David Kimchi’s ספר השרשים or Liber Radicum” (1838-48), in collaboration with F. S. Lebrecht; “The Thirty-nine Articles of the Church of England” (1840); “The Book of Psalms,” Hebrew text and Commentary (1841); “The Book of Isaiah,” Hebrew Text and Commentary (1841); “Chrestomathia Rabbinica Sive Libri Quatuor, etc.” (1844); “Menachem ben Serug’s Hebrew Lexicon” (1847); “Theologisch-Historische Studien” (1847); “Zur Geschichte der Christlichen Kirche,” etc. (1850); “Das Trostschreiben des Apostels Paulus an die Hebraer” (1878); and a Hebrew Translation of the Epistles to the “Hebrews and the Romans,” with Commentary (1857-8). He also wrote Commentaries on “St. Matthew’s Gospel, the Acts of the Apostles,” an Essay on “The Atonement”; and the “Life of Gerson.”
In 1877, the University of Giessen conferred upon him the degree of Doctor of Divinity.
In his greatest work, the “History of the Christian Church,” intended for the special use of the Jews, he proved that they stood in close connexion with the early Church, by bringing prominently forward the history of Jewish believers who loved their Saviour devotedly and laboured successfully for the spread of the Gospel at the time of its first promulgation.
Prayer:Blessed are You, HaShem, our God, King of the Universe,
who has given of His knowledge to flesh and blood.
Blessed are You, HaShem, our God, King of the Universe,
who has apportioned of His knowledge to those who revere Him.
Thank you, Lord, for the life and work of Raphael Hirsch – his lasting contribution of scholarship and his effective witness to the Messiah. Lord, we need men and women of his gifts and character today. Help us to study his work, and study his life and character, so that those fruits of knowledge, wisdom and grace may be manifested in our lives also. In Yeshua, the living Word of truth, we pray. Amen.
the Talmudical warning—”Keep your children from the study of Holy Scripture,”
WTF are you talking about?!?!? Where is this supposed Talmudic warning?
Good q – I think he mean the talmudic warnings against the gospels – awon gilion – evangelion – see https://en.wikipedia.org/wiki/Gilyonim