Here we have, 1. David's dread of the risings of sin, and the first beginnings of it: I hate vain thoughts. He does not mean that he hated them in others, for there he could not discern them, but he hated them in his own heart. Every good man makes conscience of his thoughts, for they are words to God. Vain thoughts, how light soever most make of them, are sinful and hurtful, and therefore we should account them hateful and dreadful, for they do not only divert the mind from that which is good, but open the door to all evil, Jer 4:14. Though David could not say that he was free from vain thoughts, yet he could say that he hated them; he did not countenance them, nor give them any entertainment, but did what he could to keep them out, at least to keep them under. The evil I do I allow not. 2. David's delight in the rule of duty: But thy law do I love, which forbids those vain thoughts, and threatens them. The more we love the law of God the more we shall get the mastery of our vain thoughts, the more hateful they will be to us, as being contrary to the whole law, and the more watchful we shall be against them, lest they draw us from that which we love.