Imam al-Shafi'i (may Allah have mercy on him) said: "In the time of the Messenger of Allah (peace and blessings be upon him), Sayyiduna Safwan bin al-Mu'attal (may Allah be pleased with him) struck Sayyiduna Hassan bin Thabit (may Allah be pleased with him) a severe blow with a sword, yet Sayyiduna Safwan (may Allah be pleased with him) did not have (his hand) cut off; and Sayyiduna Hassan (may Allah be pleased with him) pardoned him after he recovered, so the Messenger of Allah (peace and blessings be upon him) did not punish Sayyiduna Safwan (may Allah be pleased with him) at all."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / Q16057