Imam al-Shafi'i (may Allah have mercy on him) said: "Allah, the Blessed and Exalted, says: 'But whoever gives it (the retaliation) up as charity (pardons it), it will be an expiation for him.' [Surah al-Ma'idah: 45]"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / Q16047