John Gill Commentary Hebrews 1:13

"But of which of the angels hath he said at any time, Sit thou on my right hand, Till I make thine enemies the footstool of thy feet?" — Hebrews 1:13 (ASV)

But to which of the angels said he at any time
That is, he never said to any of them in his council, or covenant; he never designed to give them any such honour, as hereafter expressed; he never promised it to them, or bestowed it on them; he never called up any of them to so high a place, or to such a dignity:

sit on my right hand, until I make your enemies your footstool ;
yet this he said to his Son, (Psalms 110:1) for to him, the Messiah, are they spoken, and have had their fulfilment in him: (See Gill on Matthew 22:44); and therefore he must be greater than the angels.