Albert Barnes Commentary Titus 3:9

"but shun foolish questionings, and genealogies, and strifes, and fightings about law; for they are unprofitable and vain." — Titus 3:9 (ASV)

But avoid foolish questions and genealogies. (See the notes on 1 Timothy 1:4; also on 2 Timothy 2:16 and 2 Timothy 2:23.)

And contentions, and strivings about the law—such as the Jews initiated concerning various matters connected with the law, about meats and drinks, and so on. (See the notes on 1 Timothy 1:4.)

Compare the notes on Acts 18:15.

For they are unprofitable and vain. They disturb and embitter feelings; they lead to indulging a bad spirit; they are often difficult to settle and are of no practical importance, even if they could be resolved. The same thing could be said of many things about which people dispute so earnestly today.