Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) said regarding this saying of Allah Almighty, "whoever gives it up as charity, it will be an expiation for him" [Surah al-Ma'idah: 45]: That is, sins of his equal to it are removed from him. Imam al-Shafi'i (may Allah have mercy on him) said: It is narrated from the Messenger of Allah (peace and blessings be upon him) concerning pardoning retaliation that "it becomes an expiation," or he said that "there is encouragement in it to pardon retaliation."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16048