Says the Shaykh Abu Ja'far: Our belief concerning the Promise (al-wa'd) and the Threat (al-wa'id) 1 is that he whom Allah promises a reward for his good actions will certainly receive it. But he whom Allah has threatened with a punishment may have an alternative. If He punishes him, it is His justice; but if He forgives, it is His generosity.2
“And thy Lord is not unjust towards His slaves” (Qur'an 41:46).
And He says, Mighty and Glorious is He:
“Lo! Allah forgiveth not that a partner should be ascribed unto Him. And He forgiveth (all) save that to whom He will” (Qur'an 4:116).
And Allah knows best.