Q. Can a convert to Judaism describe the Almighty in his prayers as the God of his fathers?
A. It seems from the Mishnah (Bikkurim 1:4) that on the festival of Shavu’ot when the first fruits are brought to the Temple (Deut. 26:3), a convert cannot say the declaration which speaks of the land which God promised “to our fathers”.
There is evidence from Maimonides, however, that this is not the last word, and the convert may refer to “our fathers” like every other Israelite, and that on Pesach he may aver that God “passed over the houses of our fathers”.
The “fathers” are Abraham and his descendants, and Abraham is called in the Torah the “father of many nations” (Gen. 17:4). So even if the convert did not personally have a Jewish father, he can still acknowledge parentage from Abraham.
Maimonides is adamant that a convert is “like any other Israelite with regard to all matters” (Mishneh Torah, Hil’chot Issurei Bi’ah 12:17).