Imam al-Shafi'i (may Allah have mercy on him) said: "Tulayhah killed Sayyiduna Ukkashah bin Mihsan and Sayyiduna Thabit bin Aqram (may Allah be pleased with them both), then he accepted Islam, and he was not held liable for either blood money (diyah) or retaliation (qisas)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / Q16760
Al-Zuhri (may Allah have mercy on him) says: When Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) became caliph and the Arabs apostatised, he sent Sayyiduna Khalid bin al-Walid (may Allah be pleased with him) to fight them. Tulayhah was fierce in battle, and he killed Sayyiduna Ukkashah bin Mihsan (may Allah be pleased with him) and Sayyiduna Ibn Aqram (may Allah be pleased with him). Later he became Muslim, came to Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) in Madinah, and then went to Makkah and performed Umrah. It is mentioned from Ata' bin Abi Rabah that he waived the retaliation (qisas) for him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16760