What does Matthew 23:17 mean?

Israel's religious leaders are being condemned by Christ for the practice of using deceptive, layered "oaths" when making promises. As part of that error, these men suggested an oath made on some things related to God were not binding, while oaths made on other things were legitimate. He began with their position that an oath made on the temple is not binding, but an oath made on the gold in the temple is binding (Matthew 23:16).

Jesus now calls them blind fools (Matthew 15:12–14; John 9:39–41) for inventing these distinctions. Asking a rhetorical question, Jesus distinguishes between the gold and that which would make the gold sacred? Do the Pharisees think the gold is more valuable because it is worth more earthly money, or do they see the gold as sacred because it is in the temple? If it's the latter, that should make the temple itself far more valuable. Jesus condemns their valuation of gold and of the temple.

At the same time, Jesus is repeating an earlier criticism, condemning the practice of offering extra promises on top of one's sincere word. In this case, the Pharisees even taught that one such oath should be binding, while others were not. Making that distinction could only encourage taking meaningless oaths—a premeditated intent to break one's word. As Jesus taught in the Sermon on the Mount, the proper thing is to give any promise in simple terms and then keep it, no extra guarantees needed (Matthew 5:33–37).