Albert Barnes Commentary Deuteronomy 29:19

"and it come to pass, when he heareth the words of this curse, that he bless himself in his heart, saying, I shall have peace, though I walk in the stubbornness of my heart, to destroy the moist with the dry." — Deuteronomy 29:19 (ASV)

On this thought, compare Jeremiah 23:17. The secret and presumptuous sinner is meant, who flatters himself that all is well and will be well with him, since he follows his own devices and prospers. Compare Psalms 73:11 and following.

To add drunkenness to thirst - The meaning is probably: “Himself, drinking iniquity like water (Job 15:16), he corrupts and destroys others who are thirsting for it or prone to it.”

The sense of the whole passage from Deuteronomy 29:16 onward to Deuteronomy 29:20 may be presented as follows: “You have seen the abominations of idolatry among the pagans. Therefore, look diligently to ensure that there is no secret idolater among you—a root of bitterness to all around him. Let there be no one, I say, who, when he hears the curses of the Law against this sin, flatters himself, saying within himself, ‘All will be well, for I walk unmolested in my own self-chosen path;’ and by acting this way, not only takes his own fill of sin but also destroys every tempted brother within his reach, for the Lord will not spare him,” and so on.