Surah 64. At-Taghabun, Ayah 6

Lit., "guide us". This negative response is characteristic of people who, in result of their own estrangement from all moral standards, are instinctively, and deeply, distrustful of all things human and cannot, therefore, accept the idea that a divine message could manifest itself through mere human beings that have nothing "supernatural" about them.

I.e., apostles from their own midst, entrusted with divine messages specifically meant for them. The expression "time and again" is conditioned by the phrase kanat ta'atihim, which implies repetition and duration.

Their obedience is not necessary to Allah, nor will their rejection of Truth affect the validity of Truth or injure the progress of Truth. Allah is free of all needs or dependence on any circumstance whatever. He sends His Message for the good of mankind, and it is man who suffers by ignoring, rejecting, or opposing it.

This is referred to in a more expanded form in xiv. 9-11, which see.