I heard that once being a Jew was not based on the mother, it was based on the father. But I don’t know where there are sources for this and it is quite important to me. If you do know, I would be happy to find the sources for patrilineal Judaism.
Two revolutionary changes were introduced by Chazal in defining the “Jewish tribe” or, to be more precise, in defining the religious Jewish community:
1. They change the requirement for tribal affiliation from the father to the mother.
2. They created new laws for those who wished to join the religious Jewish community (conversion).
1. Scriptural Judaism emphasized, the whole way through, the father as the continuance of Judaism, not the mother. The Scriptures emphasize: “and they were registered by the clans of their fathers’ houses” (Numbers 1:18). This fact needs no proof, for anyone who reads the Tanach will find only relationships between fathers and children; for the most part the mother is not even mentioned. See, for example, King David’s lineage.
This is the lineage of Peretz: Peretz begot Hezron, Hezron begot Ram, Ram begot Amminadab, Amminadab begot Nahshon, Nachshon begot Salmon, Salmon begot Boaz [who married Ruth the Moabite], Boaz begot Obed, Obed begot Jesse, and Jesse begot David. (Ruth 4)
If you continue the lineage of David you will see that David married Ma’akah the daughter of Talmai king of Geshur and their son was Abshalom (II Samuel 3:3). There are many other such examples in the Scriptures.
But Chazal, for reasons known only to them, their time, and their locale, decided to change the situation and ruled a person’s being “Jewish” based on the mother, in contrast to the Scriptural rule. To keep themselves from being seen as deniers of the Scriptures Chazal applied the power of “medrash” — a method of exegesis through medrash which uproots and negates the simple meaning of the Scriptures. See our answer In the Scriptures, the children are related to the father.
2. The Scriptures do not detail the process of conversion or joining the Israelite nation. It uses the simple language “admitted to the congregation” (Deuteronomy 23:9) without explaining how this happens. Chazal, as was their wont, “demand” that which they wish and decided that the conditions for joining the Jewish religion are circumcision, immersion in a ritual bath, and the bringing of a sacrifice. See uor answer Conversion is a covenant with G-d and not a means of joining the Jewish nation.
With the hope that the Israeli public will gather its courage and spirit to change the laws of immigration and personal laws, both of which are based on the whims and demands of Chazal,