If Messianic Judaism was strictly Jewish at first, how did Gentiles come into the faith?
It was always God’s will for the Gentile nations to also receive His Salvation (Is. 49:6, 42:6). God told Abraham, that through him all the nations of the earth would be blessed (Gen. 12:1-3). At first, the early Messianic Jews did not understand that this was God’s will and proclaimed the Good News of the Messiah only to Jewish people.
Ironically, the big controversy in the first century was not if it was Jewish to believe in Yeshua (naturally it was) but whether Gentiles could come in without having to “become Jewish!” When Messianic Jews finally recognized that God’s Salvation was also for the Gentiles, they began to share the Messiah with non-Jews as well as with Jews. As a result, many Gentiles throughout the Roman Empire began to come into this Messianic faith (Acts 15:1-31).