Parshat Ki Tavo (Dvarim 26:1-11) opens with the Declaration of the Bikurim (First Fruits):
When you come to the land that the Lord, your God is giving you as territory and you inherit it and settle it, you shall take of the first of all of the fruits of the soil that you bring from your land, that the Lord, your God is giving you and place it in a basket; and go to the place that the Lord, your God, chooses to house His presence there. You are to come to the kohen who will be of service during those days and you will say to him, “I declare today to the Lord, your God that I have come into the land that the Lord swore to our ancestors to give us.”
Would a convert be permitted to recite this declaration?
The Mishna in Bikurim 1:4 states that a convert would bring the Bikurim, but they would not recite “that the Lord swore to our ancestors to give us.”
Kehati clarifies the mishna’s reasoning: He would have to leave those words out since his ancestors were not Israelites.
The mishna continues:
When the convert prays privately he says “the God of the fathers of Israel” (instead of “God of our fathers”). When he is in the synagogue (and leads the service), he says “God of your fathers.”
According to the Rambam, Bikurim 4:3, the Halacha does not follow the mishna above but rather Rabbi Yehuda’s opinion in the Talmud Yerushalmi, Bikurim 1:4:
The convert brings the Bikurim and recites the declaration as is stated regarding Avraham (Breisheet 17:5) “For I have made you the father of a multitude of nations.” Avraham is the father of all nations who come to shelter under the wings of the Divine Presence. Furthermore, it was to Avraham that the divine oath was first sworn that his children would possess the Land.
Ramban, Rashba and Ritva all follow Rambam’s opinion that the convert would recite the Declaration of the Bikurim and says “Our God and the God of our fathers” when reciting Shmoneh Esrei both privately and publicly.
This question can also arise when a convert recites the second paragraph of Birkat HaMazon, the Grace After Meals, “Nodeh Lecha,” “We thank you , the Lord our God, because you have given to our forefathers as a heritage a desirable good and spacious land…”
Would a convert be permitted to say “L’Avotaynu,” “to our forefathers” in Birkat HaMazon?
The Land of Israel was promised to Avraham and his descendents and converts are considered to be the children of Avraham. In fact, when a person converts to Judaism, they are referred to as the child of Avraham Avinu. According to Shu”t HaRambam 296 there should be no difference between any of the prayers that a born Jew recites and the prayers that a convert recites.
May the Declaration of Bikurim remind us that once a person converts to Judaism they are considered a full fledged Jew and they should not be singled out.