Musannaf Ibn Abi Shayba 21:311

Al-Fadl narrated to us, Sufyan informed us, from Shabib ibn Gharqada, from Muhammad ibn Amr ibn Ata, who said: The Prophet, peace and blessings of Allah be upon him, said to Sawda: "Glorify Allah (say SubhanAllah) every morning ten times, and magnify Him (say Allahu Akbar) ten times, and praise Him (say Alhamdulillah) ten times, and say 'Forgive me' (Astaghfirullah) ten times. For He says: 'I have done so, I have done so.'"