Compare on the thought 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 ff.
To add drunkenness to thirst - The sense 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 exhibited thus: “Ye have seen the abominations of idolatry among the pagan. Do you therefore look diligently that there be no secret idolater among you; a root of bitterness to all about 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 thus acting, not only takes his own fill of sin, but destroys likewise every tempted brother within his reach, for the Lord will not spare him,” etc.