Surah 47. Muhammad, Ayah 9

Namely, the revelation relating to man's moral responsibility to a Supreme Being.

The particle fa ("and thus") at the beginning of this clause connotes a consequence: in other words, it is their rejection of the idea of moral responsibility, inherent in all divine revelation, that deprives the deeds of "those who are bent on denying the truth" - even such deeds as might be termed "good" - of all moral value. This law of inner causality explains fully the phrase "He will let all their [good] deeds go to waste" occurring in verses {1} and {8}.

Their deeds are "fruitless" in the sense that they are vain; they do not produce the results intended by their doers. But they will not be exempt from producing the natural consequences of evil, viz., further degradation and misery for the soul.