Reference: Ibn Battaal in his explanation of al-Bukhaaree, 6/575
al-Hasan al-Basree supplicated one night, saying:
Oh Allaah forgive whomsoever oppressed me.
…and he increased in [supplicating for] that.
So a man said to him:
Oh Abaa Sa’eed, indeed I heard you supplicating this night for the ones who oppressed you, until I wished to be amongst them. What led you to do this?
He said:
His – the Most High – saying:
{…but whoever forgives and makes reconciliation, his reward is due from Allaah.} [soorah ash-Shooraa, aayah 40]