Does the prayer become void if the worshipper intentionally says "no" during the prayer, while forgetting that he is praying or that speech invalidates it?

If one speaks a few words forgetfully while praying, their prayer is not invalidated by that according to the majority of scholars. Among those who held this view are Ibn Mas'ud, Ibn Abbas, Malik, and Ahmad. Therefore, your prayer is not invalidated by the word you uttered out of forgetfulness. Ignorance refers to not knowing the ruling concerning one who speaks during their prayer.