Church Fathers on Luke 16:17

Christ had told the Pharisees not to boast of their own righteousness, but to receive penitent sinners, and to redeem their sins by almsgiving. But they derided the Preacher of mercy, humility, and frugality; as it is said, And the Pharisees also, who were covetous, heard these things; and derided him: it may be for two reasons, either because He commanded what was not sufficiently profitable, or cast blame upon their past superfluous actions.

But the Lord detecting in them a hidden malice, proves that they make a presence of righteousness. Therefore it is added, And he said to them, you are they which justify yourselves before men.

Not that the Law failed, but that the preaching of the Gospel began, for that which is inferior seems to be completed when a better succeeds.