Abba Tsabrah (traditional attribution)

Abba Tsabrah (also, Abba Sabra, fl. ca. 1450) was an Ethiopian Orthodox monk and the teacher of the children of Emperor Zara Yaqob of Ethiopia who became a prominent and influential Jewish convert. Abba Tsabrah tried to convert the Beta Israel (Ethiopian Jews) to Christianity, but was instead converted by them to Judaism. He then later converted the son of king Zara Yaqob, Saga-Amlak, who adopted the religious name Abba Saga. Later Abba Tsabrah and Abba Saga established a separate kingdom in modern day Ethiopia in which Jews were not persecuted. Tsabrah is also known for introducing monasticism to the Beta Israel, and the tradition of Jewish monks continued down the centuries until the Great Famine of the 1890s decimated their monasteries in Lay Armachiho.

https://en.wikipedia.org/wiki/Abba_Sabra