Musnad Ahmad 154:14

Yunus narrated to us, Laith narrated to us, from Yazid—meaning Ibn al-Had—from Isma'il ibn 'Abdullah ibn Ja'far, who said: It reached me that the Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no person who is in a gathering, then says when he intends to stand up: 'Glory be to You, O Allah, and with Your praise; there is no god but You; I seek Your forgiveness and I repent to You,' except that what occurred in that gathering is forgiven for him." I narrated this hadith to Yazid ibn Khusaifah, and he said: "Thus did al-Sa'ib ibn Yazid narrate to me, from the Messenger of Allah (peace and blessings of Allah be upon him)."