The Arab invasion of Egypt at first found support from Jewish residents as well, disgruntled by the corrupt administration of the Patriarch Cyrus of Alexandria, notorious for his Monotheletic proselytizing. In addition to the Jewish population settled there from ancient times, some are said to have come from the Arabian Peninsula. The letter sent by Muhammad to the Jewish Banu Janba in 630 is said by Al-Baladhuri to have been seen in Egypt. A copy, written in Hebrew characters, has been found in the Cairo Geniza.