Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 12:35-40

“But Christ shews Himself to be the Lord, by the words of David. For it goes on: For David himself said by the Holy Ghost, The Lord said to my Lord, Sit thou on my right hand; as if He had said, Ye cannot say that David said this without the grace of the Holy Spirit, but he called Him Lord in the Holy Spirit; and that He is Lord, he shews, by this that is added, Till I make thine enemies thy footstool; for they themselves were His enemies, whom God put under the footstool of Christ.”