Surah 16. An-Nahl, Ayah 50

I.e., they must, by virtue of their nature, obey the impulses implanted in them by God and are, therefore, incapable of what is described as "sinning". Man, however, is fundamentally different in this respect. In contrast with the natural sinlessness of "every beast that moves, and the angels", man is endowed with free will in the moral sense of this term: he can choose between right and wrong - and therefore he can, and often does, sin. But even while he sins he is subject to the universal law of cause and effect instituted by God and referred to in the Qur'an as sunnat Allah ("God's way"): hence the Qur'anic statement that "before God prostrate themselves, willingly or unwillingly, all [things and beings] that are in the heavens and on earth" ( 13:15 ).

 The angels.

Allah is so high above the highest of His creatures, that they all look up to him in awe and reverence. And they joyfully do their duty in serving Him. This is the meaning of the "fear of the Lord."