Maimonides was once asked by a proselyte whether it was proper for a proselyte to say "Our fathers" in Jewish liturgy when, in reality, a proselyte is probably not descended from Avraham, Yitzchak, and Ya'akov. You can see Maimonides response HERE. He thought it was perfectly acceptable for a proselyte to say this. And on what basis did he feel it was acceptable?
"Yes, you may say all this in the prescribed order and not change it in the least. In the same way as every Jew by birth says his blessing and prayer, you, too, shall bless and pray alike, whether you are alone or pray in the congregation. The reason for this is, that Abraham our Father taught the people, opened their minds, and revealed to them the true faith and the unity of God; he rejected the idols and abolished their adoration; he brought many children under the wings of the Divine Presence; he gave them counsel and advice, and ordered his sons and the members of his household after him to keep the ways of the Lord forever, as it is written, “For I have known him to the end that he may command his children and his household after him, that they may keep the way of the Lord, to do righteousness and justice” (Gen. 18:19)...
...because since you have come under the wings of the Divine Presence and confessed the Lord, no difference exists between you and us, and all miracles done to us have been done as it were to us and to you. Thus is it said in the Book of Isaiah, “Neither let the son of the stranger, that has joined himself to the Lord, speak, saying, ‘The Lord has utterly separated me from His people’” (Is. 56:3). There is no difference whatever between you and us. You shall certainly say the blessing, “Who has chosen us,” “Who has given us,” “Who have taken us for Your own” and “Who has separated us”: for the Creator, may He be extolled, has indeed chosen you and separated you from the nations and given you the Torah. For the Torah has been given to us and to the proselytes, as it is said, “One ordinance shall be both for you of the congregation, and also for the stranger that sojourns with you, an ordinance for ever in your generations; as you are, so shall the stranger be before the Lord” (Num. 15:15). Know that our fathers, when they came out of Egypt, were mostly idolaters; they had mingled with the pagans in Egypt and imitated their way of life, until the Holy One, may He be blessed, sent Moses our Teacher, the master of all prophets, who separated us from the nations and brought us under the wings of the Divine Presence, us and all proselytes, and gave to all of us one Law," (from Maimonides letter to Obadiah the Proselyte).We also see that Paul encouraged non-Jews to identify with G-d's People:
"For I do not want you to be unaware, brethren, that our fathers were all under the cloud and all passed through the sea," (1 Cor. 10:1)Maimonides believed that just as the Name is unified so also is the faith unified in that there is "one law" for all those included in His People. And how did one know he was included in the People of Israel? According to Maimonides, this inclusion is connected to coming under the "Divine Presence."
So why did Paul include non-Jews into the People by saying "Our" fathers?
Well, in Acts 15 Paul made the case that the non-Jews had come under the Divine Presence:
"The whole assembly became silent as they listened to Barnabas and Paul telling about the signs and wonders God had done among the Gentiles through them," (Acts 15:12)
And in 1 Corinthians 12:
"For we were all baptized by one Spirit into one body--whether Jews or Greeks, slave or free--and we were all given the one Spirit to drink."Here's a few more:
"While Apollos was at Corinth, Paul took the road through the interior and arrived at Ephesus. There he found some disciples and asked them, "Did you receive the Holy Spirit when you believed?" They answered, "No, we have not even heard that there is a Holy Spirit." So Paul asked, "Then what baptism did you receive?" "John's baptism," they replied. Paul said, "John's baptism was a baptism of repentance. He told the people to believe in the one coming after him, that is, in Jesus." On hearing this, they were baptized into the name of the Lord Jesus. When Paul placed his hands on them, the Holy Spirit came on them, and they spoke in tongues and prophesied," (Acts 19:1-6)
"And afterward, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions. Even on my servants, both men and women, I will pour out my Spirit in those days," (Joel 2:28-29)CONCLUSION
Of course Maimonides disagreed with Paul that uncircumcised non-Jews could be included in G-d's People and the rule of One-Law. But Maimonides only disagreed because he failed to grasp that non-Jewish Believers in Yeshua come under the Divine Presence! So Maimonides and Paul both agreed to the basic idea that to be joined to HaShem was to be joined to His People (and the One Law).