Surat Al-Shuraa (42:40):
وَجَزَاء
سَيِّئَةٍ سَيِّئَةٌ مِّثْلُهَا فَمَنْ
عَفَا وَأَصْلَحَ
فَأَجْرُهُ
عَلَى اللَّهِ
إِنَّهُ لَا يُحِبُّ الظَّالِمِينَ
(
And
the retribution for an evil act is an evil one like it, but whoever
pardons and makes reconciliation - his
reward is [due] from Allah.
Indeed, He does not like wrongdoers.
What
does this mean; that his ajr/reward rests with Allah?
It
means; "The pages of the Quran are unable to hold this
ajr/reward that is mentioned. That, also the dunya/world and
everything within it could not carry this ajr so that it can be
mentioned. So Allah (swt) preserved it in Ilm AL-Ghayb [the knowledge
of the Unseen] so that he can reward those who forgive/pardon others
and make peace with them with an unimaginable reward!