Charles H. Spurgeon on Psalms 109:7

Let his prayer become sin. The prayer of the hypocrite is sin formally, and it is sin in the effect, that is, instead of getting any good by it, he gets hurt, and the Lord instead of helping him because he prays, punishes him because of the sinfulness of his prayers. Thus his prayer becomes sin to him, because he receives no more respect from God when he prays than when he sins. And sin doth not only mingle with his prayer (as it doth with the prayers of the holiest), but his prayer is nothing else but a mixture or mingle mangle (as we speak) of many sins. —Joseph Caryl.