Concise Bible Dictionary:

These were the records of generations: “the genealogy of their generations” was reckoned (1 Chron. 5:77And his brethren by their families, when the genealogy of their generations was reckoned, were the chief, Jeiel, and Zechariah, (1 Chronicles 5:7); 1 Chron. 7:99And the number of them, after their genealogy by their generations, heads of the house of their fathers, mighty men of valor, was twenty thousand and two hundred. (1 Chronicles 7:9)). Though “generations” are given from the beginning, we do not read of “genealogies” until Israel was in the land. It was important then that the genealogies should be preserved, because it was a part of the law that the children of Israel should enjoy every man the inheritance of his fathers. The inheritance must not remove from tribe to tribe (Num. 36:8-98And every daughter, that possesseth an inheritance in any tribe of the children of Israel, shall be wife unto one of the family of the tribe of her father, that the children of Israel may enjoy every man the inheritance of his fathers. 9Neither shall the inheritance remove from one tribe to another tribe; but every one of the tribes of the children of Israel shall keep himself to his own inheritance. (Numbers 36:8‑9)). As the priesthood was restricted to the sons of Aaron, it was essential that they should preserve their genealogy. On the return from the exile some were unable to show their descent from Aaron, and they were put out of the priesthood (Ezra 2:6262These sought their register among those that were reckoned by genealogy, but they were not found: therefore were they, as polluted, put from the priesthood. (Ezra 2:62)).
A knowledge of the priestly genealogies extended to the New Testament. Zacharias was of the “course of Abia,” and Elizabeth was “of the daughters of Aaron.” So also of the tribes and families generally. At the census Joseph and Mary went to Bethlehem, for they were of the lineage of David; Anna was of the tribe of Asher, and Paul of the tribe of Benjamin.
It is probable that in 1 Timothy 1:44Neither give heed to fables and endless genealogies, which minister questions, rather than godly edifying which is in faith: so do. (1 Timothy 1:4) and Titus 3:99But avoid foolish questions, and genealogies, and contentions, and strivings about the law; for they are unprofitable and vain. (Titus 3:9) reference is not made to Jewish genealogies, which could not be called “endless,” nor were they fabulous; but that reference is made to the eons of the Gnostics which reach back to eternity, three of which were represented to be Christ, the Holy Spirit, and Jesus. Tertullian quoted the above passage in Timothy when confuting the Gnostics.