Musnad Ahmad 788:188

Waki’ narrated to us, Mughirah al-Kindi narrated to us, from Sa’id ibn Abi Burdah, from his father, from his grandfather, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Verily, I seek forgiveness from Allah, the Almighty and Majestic, one hundred times every day." ‘Abdullah said: He means Mughirah ibn Abi al-Hurr.