Albert Barnes Commentary Matthew 23:21

"And he that sweareth by the temple, sweareth by it, and by him that dwelleth therein." — Matthew 23:21 (ASV)

Him that dwelleth therein. That is, God. The temple was His house, His dwelling. In the first, or Solomon's temple, He dwelt between the cherubim, in the most holy place. He manifested Himself there by a visible symbol, in the form of a cloud resting on the mercy seat, 1 Kings 8:10, 13; Psalms 80:1.