Surah 67. Al-Mulk, Ayah 13

I.e., He knows why one person believes in Him and another rejects this belief; hence, He takes man's innermost motivations, abilities and inabilities fully into account.

While the primary significance of the noun qawl is "a saying" or "an utterance", it is often used tropically in the sense of "a statement", i.e., of a belief, an opinion, a teaching, a doctrine, etc. In the present context it evidently relates to man's beliefs in general, be they affirmative or negative: hence the plural form in my rendering of this term.