Deuteronomy 29:18

והתברך בלבבו AND HE BLESS HIMSELF IN HIS HEART — The word והתברך has the meaning of “blessing”. In his heart he will imagine for himself a blessing of peace, saying, “These curses will not come upon me, I shall have peace”. והתברך is benoir soi in old French, i.e. the verb is reflexive like והתגלח, “he shall shave himself”, והתפלל, he shall pray lit., he shall make himself the object of intercession. בשררות לבי אלך means IN THE VIEWS OF MY HEART WILL I WALK, שררות being of a root which means to look, to see, as (Numbers 25:17): “I shall see him (אשרנו), but not now”; it is as much as to say, I will follow what my heart sees good to do. למען ספות הרוה TO ADD DRUNKENNESS [TO THE THIRST] — In order that I may add punishment for him even for the sins he has committed until now inadvertently (for which the figurative expression in this sentence is הרוה, drunkenness: cf. the following passage in Rashi), and which I used to overlook; — but now he causes Me to combine them with those committed with premeditation and to exact punishment from him for everything. Onkelos, too, rendered it in a similar sense: “in order to add for him the sins of inadvertence to those of premeditation”, which can only mean. “In order that “I” may add sins of inadvertence to those of presumption”. הרוה DRUNKENNESS figuratively describes the condition of a שוגג, one who acts inadvertently. The expression is an apt one because he acts like a drunken man who does things unwittingly, הצמאה THE THIRST aptly describes the attitude of one who acts wittingly and out of desire.

וְהָיָ֡ה בְּשׇׁמְעוֹ֩ אֶת־דִּבְרֵ֨י הָאָלָ֜ה הַזֹּ֗את וְהִתְבָּרֵ֨ךְ בִּלְבָב֤וֹ לֵאמֹר֙ שָׁל֣וֹם יִֽהְיֶה־לִּ֔י כִּ֛י בִּשְׁרִר֥וּת לִבִּ֖י אֵלֵ֑ךְ לְמַ֛עַן סְפ֥וֹת הָרָוָ֖ה אֶת־הַצְּמֵאָֽה׃

and it come to pass, when he hears the words of this curse, that he bless himself in his heart, saying, I shall have peace, though I walk in the stubborness of my heart, to add drunkenness to thirst: