Musannaf Ibn Abi Shayba 21:207

Jarir narrated to us, from Mansur, from Fudayl ibn Amr, from Ziyad ibn al-Husayn, who said: I entered upon Abu al-Aliyah. When I wanted to leave from his presence, he said: "Shall I not provide you with words that Gabriel taught to Muhammad, may Allah bless him and grant him peace?" I said: "Yes." He said: "When it was at the end, whenever he would stand up from his gathering, he would say: 'Glory be to You, O Allah, and with Your praise. I bear witness that there is no god but You. I seek Your forgiveness and I repent to You.' It was said: 'O Messenger of Allah, what are these words that you say?' He said: 'They are words that Gabriel taught me, as expiations for what occurs in the gathering.'"