And he answered and said, Must I not take heed to speak that which the LORD hath put in my mouth?

Wesley's Notes

23:12 Must I not - Ought I not? Is it not my duty? Canst thou blame me for it?

Matthew Henry's Concise Commentary

23:11-30 Balak was angry with Balaam. Thus a confession of God's overruling power is extorted from a wicked prophet, to the confusion of a wicked prince. A second time the curse is turned into a blessing; and this blessing is both larger and stronger than the former. Men change their minds, and break their words; but God never changes his mind, and therefore never recalls his promise. And when in Scripture he is said to repent, it does not mean any change of his mind; but only a change of his way. There was sin in Jacob, and God saw it; but there was not such as might provoke him to give them up to ruin. If the Lord sees that we trust in his mercy, and accept of his salvation; that we indulge no secret lust, and continue not in rebellion, but endeavour to serve and glorify him; we may be sure that he looks upon us as accepted in Christ, that our sins are all pardoned. Oh the wonders of providence and grace, the wonders of redeeming love, of pardoning mercy, of the new-creating Spirit! Balak had no hope of ruining Israel, and Balaam showed that he had more reason to fear being ruined by them. Since Balaam cannot say what he would have him, Balak wished him to say nothing. But though there are many devices in man's heart, God's counsels shall stand. Yet they resolve to make another attempt, though they had no promise on which to build their hopes. Let us, who have a promise that the vision at the end shall speak and not lie, continue earnest in prayer, Lu 18:1.