Once at Acre, he was reminded by its rabbi of his insufficient knowledge of the Jewish religion; and he left the city (1226), resolving to abandon commerce and to devote himself exclusively to rabbinical and scientific studies.
Shem-Ṭob's first work was his Hebrew translation, under the title of Bi'ur Sefer ha-Nefesh, of Averroes' middle commentary on Aristotle's De Anima.
In the month of Elul, 1254, at the age of fifty-eight, he began the translation into Hebrew of Al-Zahrawi's Kitab al-Taṣrif, a medical work in thirty books.
This translation is preceded by a long introduction, which forms a treatise in itself, and in which he deals with man as composed of four elements, and with the relation between diseases and the four seasons of the year.
De Castro concludes this from the date 1267, which is given in the Escorial manuscript of the work in question and which is a century earlier than the time of Shem-Ṭob ibn Shaprut.