86. " how shall allah guide a people who have disbelieved after their belief and
(after) bearing witness that the messenger is true,
and clear proofs had come unto them ?
and allah guides not the unjust people."

occasion of revelation
at the advent of islam, one of the helpers (the muslims in medina)
murdered a sinless person. being afraid of the punishment, he apostatized
and escaped to mecca, while eleven persons of his companions, who had
embraced islam, apostatized, too. when he arrived in mecca, he repented
of his action seriously. then, he sent one of his relatives to medina to ask
the prophet (p.b.u.h.) whether there was any way for him to return.

the verse was revealed and announced the acceptance of his
repentance under some special conditions.

commentary:
in the former verses, the speech was about the religion of islam as a
godly acceptable religion. here, the verse speaks about the persons who
have accepted islam and, afterward they have returned from it. these
persons are called `apostates'.
it says:

" how shall allah guide a people who have disbelieved after their belief and
(after) bearing witness that the messenger is true,
and clear proofs had come unto them ? and allah guides not
the unjust people."

why does allah not guide such people ? the reason of it is evident.
they have known the prophet (p.b.u.h.) through many clear signs and
tokens and, thereafter, they have testified to his prophethood.

therefore, by returning from islam to infidelity, they are, indeed,
unjust and transgrossive. so, the one who intentionally transgresses is not
eligible for the guidance of allah. such a person has spoilt the aspects of
guidance in his self.