God delayed the destruction of Sdom until Avraham had an opportunity to intercede on behalf of the city. God’s reason for involving Avraham is outlined in Parhsat Vayera, Breisheet 18:17-18:
And God said, “Shall I conceal from Avraham that thing which I intend to do; seeing that Avraham is surely to become a great and mighty nation, and the nations of the earth shall be blessed in him? For I know him, that he will command his children and his household after him that they shall keep the way of God, doing tzedaka (righteousness) and mishpat (justice); in order that God might then bring upon Avraham that which He has spoken of him.
Rambam (Maimonides) in Hilchot Avodat Kochavim 1:3 teaches: Avraham was forty years old when he recognized God. He then began to spread the word about Monotheism to the inhabitants of Ur Kasdim. He wanted to destroy all of the idols ensuring that the people would no longer have any other gods to pray to. The king of Ur Kasdim tried to kill him, yet Avraham escaped to Charan. There, he alerted the world that there is one God and he gathered followers from different cities and kingdoms until they arrived in the Land of C’naan, where he called out in the name of God. His followers would ask him questions and he would set them on the path of truth until there were thousands and then tens of thousands of followers who became known as the “house of Avraham.”
In Sheilot u’Tshuvot (Questions and Answers) 293 of the Rambam, Ovadia Ger Tzedek, a sincere convert, not biologically a descendent of Avraham asks if he can say the following parts of prayer : “Elokeinu v’Elokei Avoteinu”, “Our God and the God of our fathers” and “Shehinchalta l’Avoteinu”, “You have given (the Land of Israel) to our forefathers as a heritage.”
Rambam answers that since Avraham was the one who taught “his children and his household after him that they shall keep the way of God, doing tzedaka (righteousness) and mishpat (justice)”, everyone who converts to Judaism until the end of time as well as whoever recognizes that HaShem, our God is One is a student of Avraham and they are all considered to be the future members of his household. Just as Avraham brought the people of his generation to the right path through his teachings, so too he will also bring in all of the future converts.
Rambam concludes that Avraham is the father of his descendants who follow in his path as well as the father of all of those who convert to Judaism. Therefore, converts should not change the words of the Amida (Silent Devotion), and they should recite “Elokeinu v’Elokei Avoteinu”, “Our God and the God of our fathers” since Avraham is their “father” and in Birkat HaMazon (Grace After Meals) converts should recite “Shehinchalta l’Avoteinu”, “You have given (the Land of Israel) to our forefathers as a heritage” since Avraham was given the Land of Israel as it says (Breisheet 13:17) “Arise, walk about the Land through its length and breadth! For to you will I give it.”
May the rabbis today learn from the Rambam the importance of having respect for those who sincerely convert to Judaism.