Musnad Ahmad 335:1

Hajjaj narrated to us, he said: Shu'bah informed us, from Sa'id al-Jurayri, from Abu al-Sulayl, from an old woman of Banu Numayr, that she observed the Messenger of Allah (peace and blessings of Allah be upon him) while he was praying at al-Abtah facing the House (the Ka'bah) before the migration. She said: I heard him saying: "O Allah, forgive me my sin, my mistake, and my ignorance."