That's a good example for us to do today. Matter of fact, it's the only way we'll know for sure if a teaching is valid or not.
1 Corinthians 11:2 - I praise you for remembering me in everything and for holding to the traditions just as I passed them on to you.
Notice this is Apostolic tradition (what Paul taught), not mere "human" tradition.
Apostolic tradition is the soundest basis for determining what Scriptural (written) tradition even IS. The great Bible translator Jerome determined what books were to be included in Scripture by what books were in actual liturgical use by the Churches. Even if this contrasted with his own personal scholarly opinion, which was sometimes vehemently to the contrary.
I do think that Jaroslav Peliken put it most succinctly when he said, as regards the OT canon, that we can rely on A.D. Pharisee/tannaitic communities, councils and sources which were explicitly anti-Christian (e.g. the Rabbi Johanan ben Zakkai and his successors) --- or --- we can rely on Christian communities, councils and sources. As Jerome, finally (!), did.