Bede

Except one who has the mark, etc. That is, who shares in that deceit. For the mark, that is, the sign, and the name of the beast, and the number of his name are one. For it is the number of a man, so that we do not think, according to some opinions, that it is either the devil or a demon, but one of the men in whom Satan will dwell bodily. For he is the man of sin, the son of perdition.

Commentary on Revelation ↗