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
Sayyidah Aishah (may Allah be pleased with her) said, in the hadith of the Slander (al-Ifk): Safwan bin al-Mu'attal (may Allah be pleased with him) struck Hassan (may Allah be pleased with him) with a sword. Hassan (may Allah be pleased with him) cried out, and people came to seize Safwan (may Allah be pleased with him), and Safwan (may Allah be pleased with him) fled. Hassan (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him) and sought retribution from Safwan (may Allah be pleased with him). The Prophet (peace and blessings be upon him) said to Hassan (may Allah be pleased with him): "Grant me Safwan's retribution as a gift." So he gifted it, and in exchange he (peace and blessings be upon him) gave Hassan (may Allah be pleased with him) a large walled garden of date palms and a slave girl who was Roman, and it is said she was Coptic.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16057
Ibn Shihab (may Allah have mercy on him) was asked about a man who strikes another with a sword in anger: what should be done with him? He said: Safwan bin al-Mu'attal (may Allah be pleased with him) struck Hassan bin Thabit (may Allah be pleased with him), and the Messenger of Allah (peace and blessings be upon him) did not cut off his hand.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16058