“Whoso therefore shall swear by the altar, sweareth by it, and by all things thereon.”
Matthew 23:20 — Greek Interlinear
Church Fathers on Matthew 23:20
As by making broad phylacteries and fringes they sought after the reputation of sanctity, and made this again a means of gain, so now He charges them with being teachers of wickedness by their fraudulent pretence of tradition. For when in any dispute or quarrel, or ambiguous cause, one swore by the temple, and was afterwards convicted of falsehood, he was not held guilty. This is what is meant by that, 'Whosoever shall swear by the temple, it is nothing,' that is, be owes…
The temple pertains to God’s glory, and to man’s spiritual salvation, but the gold of the temple though it pertains to the glory of God, yet does it more so to the delight of man, and the profit of the Priests. The Jews then pronounced the gold which delighted them, and the gifts which fed them, to be more holy than the temple, that they might make men more disposed to offer gifts, than to pour out prayers in the temple. Whence the Lord suitably reproves them in these words.
And lest their infatuation should go so far, that they should affirm that the gold was more holy than the temple, and the gift than the altar, He argues on another ground, that in the oath which is sworn by the temple and the altar is contained the oath by the gold or by the gift.