4:23 What does the proverb Jesus quoted here teach?

In this proverb Jesus anticipates the Jews' demands that He perform the miracles in Nazareth that He performed in Capernaum to prove to them who He was, but Jesus was in effect telling them that His signs are only for believers, not unbelievers.

Notwithstanding that the Jews were greatly impressed by what Jesus said in Lk 4:18-21 after He read the scroll in the Synagogue, they still only saw Him as the son of the local carpenter, not the Messiah He claimed to be (cp Lk 4:16-22 with Mk 6:1-5).

Jesus knew that like other prophets before Him, He would never be accepted in His own home town (cp Lk 4:24).