Church Fathers on Luke 20:45

Now nothing is more powerful than to argue from the Prophets. For this is even of more weight than miracles themselves. For when Christ worked miracles, He was often gainsaid. But when He cited the Prophets, men were at once silent, because they had nothing to say. But when they were silent, He warns against them, as it is said, Then in the audience of all the people he said to his disciples.

For as He was sending them to teach the world, He rightly warns them not to imitate the pride of the Pharisees. Beware of the Scribes, who desire to walk in long robes, that is, to go forth into public, dressed in fine clothes, which was one of the sins remarked in the rich man.

The passions of the Scribes were the love of vainglory and the love of gain. That the disciples should avoid these hateful crimes, He gives them this warning, and adds, And love greetings in the markets.