R. Jacob b. Abraham Castro (known as Maharikas from the Hebrew initials of his name; 1525?–1610), was born in Egypt. In his youth he went to Jerusalem, where he studied under R. Levi b. Habib, and R. David b. Solomon ibn Abi Zimra. R. Castro later became rabbi of the Mustarabs in Cairo, a position he held until his death. In 1570 he visited Palestine, and was the guest of R. Joseph Caro in Safed. He maintained a regular correspondence concerning halakhic questions with such authorities as R. Caro and R. Moses di Trani. His collected responsa, Oholei Ya'akov (Leghorn, 1783), are a most important source for the history of Egyptian Jewry. Castro's novellae on several tractates of Talmud were known to the Hidah. Those on tractate Bezah were published under the title Toledot Ya'akov (1865). Hilkhot Nezirut ("Laws of Naziriteship") and Mazkeret Gittin ("Memorandum on Divorce Bills") were printed at the end of the Halakhot Ketannot of R. Jacob Hagiz (Venice, 1704). The manuscript of Castro's collected sermons, Kol Ya'akov, has been lost.

דף [2,א]: הקדמת בן... המחבר... ר' יצחק קאשטרו זלה"ה. שני הדפים הראשונים (השער, ההסכמה וההקדמות) נדפסו פעמיים (בלי שינויים בתוכן). ברוב הטפסים מסגרת השער עשויה שני עמודים מקושטים שעליהם נשענת קשת. בהדפסה השניה מסגרת השער מלבנית, מימין ומשמאל שני עמודים שעליהם מטפס בעל-חי.