The question of phraseology for a convert arises in the poskim regarding a convert in a regular minyan. Rabbeinu Tam[1] cites a mishna[2] that a convert cannot recite mikra bikurim[3] because it contains the line: “the land which HaShem swore to our fathers to give to us.”[4] Based on this, Rabbeinu Tam says that a convert cannot recite Birkat HaMazon to exempt others, since it contains a similar phrase, which is not accurate for him. Privately, he should say, “Elokei avot Yisrael” (“the Lord of the fathers of Israel”). A similar problem would exist in chazarat hashatz, both in the first beracha of Shemoneh Esrei and in Birkat Kohanim in the Diaspora, making a convert unable to be chazan.
However, the Shulchan Aruch[5] rejects this opinion and favors the view of the Ri in Tosafot.[6] Basing himself on the Yerushalmi, the Ri points out that HaShem changed Avram’s name to Avraham, connoting “father of a multitude of nations.” Thus, all converts are considered his children, and the reference to “our fathers” is a proper one.
It is arguable that the convert’s ability to use these terms should be limited to cases in which there is a specific need; this would include reciting a beracha on behalf of a Jew from birth or saying the mikra bikurim, which is a set quote from the Torah. If this were so, a minyan of converts should say, “the Lord of the fathers of Israel.” However, the implication of the Bach[7] and Mishna Berura[8] is that a convert can use the regular terminology in any setting.
It is certainly advantageous that the poskim allow converts to use the standard terminology. This helps the convert integrate more smoothly into Jewish society, as the Torah desires.