Бамидбар 23:8 Ссылки в Талмуде: Berakhot & Sanhedrin

That is the meaning of what Balaam said to Balak, "How shall I curse, whom God hath not cursed ? And how shall I execrate, whom the Lord hath not execrated?" (Num. xxiii. 8). This teaches that during all those days He did not execrate.

From where [do we know] that this [term,] nokev is an expression of ‘blessing?’ As it is written (Numbers 23:8), "What will I curse (nokev), that God did not curse" (wherein the usage of this word clearly reflects cursing); and its prohibition is from here: "God will you not curse" (Exodus 22:27).