Sayyiduna Jarir (may Allah be pleased with him) said: A man who was very fierce and formidable against the enemy was with Sayyiduna Abu Musa (may Allah be pleased with him). The spoils of war were distributed, and Sayyiduna Abu Musa (may Allah be pleased with him) gave him his share but did not give it in full. He refused to take it and demanded all of it, so Sayyiduna Abu Musa (may Allah be pleased with him) gave him 20 lashes and shaved his head. The man took his hair and came to Sayyiduna Umar (may Allah be pleased with him). Sayyiduna Jarir (may Allah be pleased with him) said: I was the closest of the people to him. He took the hair out of his pocket and struck Sayyiduna Umar (may Allah be pleased with him) on the chest with it, and he asked: "What is this?" He told him the whole story, and Sayyiduna Umar (may Allah be pleased with him) wrote to Sayyiduna Abu Musa (may Allah be pleased with him): "Amma ba'd (to proceed, after praise and glorification): So-and-so son of so-and-so has informed me of such-and-such. I adjure you by Allah: if you treated him this way in front of people, then in front of people, and if you did it in private, then in private, give him retaliation against yourself." The people said to the man: "Forgive him." He said: "Never, by Allah!" When he handed the letter to Sayyiduna Abu Musa (may Allah be pleased with him), he (may Allah be pleased with him) sat down for the retaliation, and the man raised his head to the sky and said: "I have forgiven him for the sake of Allah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16027