Matthew 23:16

Wo to you blind guides. Avarice seems to have been the chief motive of the Pharisees in teaching this doctrine, since they taught that those who swore by the temple were guilty of no sin, nor under any obligation at all; whereas they who swore by the gold of the temple, were bound to pay a certain sum of money to the priests, by which they themselves were enriched. (Nicholas de Lyra.) --- Whosoever shall swear by the temple, it is nothing, &c. To understand this obscure place, we may take notice, that a good part of what was offered on the altar, and given to the treasury of the temple, fell to the share of the Jewish priests; and therefore it was not their interest to have such promises or oaths dispensed with. This made them teach the people, that if any one had made a promissory oath or vow to give their money or goods to the temple, or to the altar itself, as it is said ver. 18, such oaths or promises were not obligatory, or might easily be dispensed with. But if any one had sworn or vowed to give any thing to the treasury of the temple, or join it to the offerings to be made on the altar, then such oaths and promises which turned to their profit were by all means to be kept. St. Jerome expounds it of oaths in common discourse; as if the taught the people, that when any one swore by the temple, or by the altar, it was not so considerable as to swear by the gold in the temple, or by the offerings there made: for in the latter cases, they were to make satisfaction according to the judgment of the Jewish priests. And to correct their covetous proceedings, Christ tells them that the temple and the altar were greater than the gold and the offerings. (Witham)