Adam Clarke on Isaiah 57:8

Behind the doors also and the posts hast thou set up thy remembrance "Behind the door, and the door-posts, hast thou set up thy memorial" - That is, the image of their tutelary gods, or something dedicated to them; in direct opposition to the law of God, which commanded them to write upon the door-posts of their house, and upon their gates, the words of God's law; Deu 6:9; Deu 11:20. If they chose for them such a situation as more private, it was in defiance of a particular curse denounced in the law against the man who should make a graven or a molten image, and put it in a secret place; Deu 27:15. An ancient MS., with another, has אחר achar, without the conjunction ו vau, and.