Musnad Ahmad 1060:21

Ishaq ibn Ibrahim al-Razi narrated to us, Salama ibn al-Fadl narrated to us, Muhammad ibn Ishaq narrated to me, from Yazid ibn Yazid ibn Jabir, from al-Qasim ibn Mukhaymirah, from Abdullah ibn Ya'ish, from Abu Ayyub al-Ansari, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever says, when he has prayed the morning prayer: 'There is no god but Allah, alone, with no partner, to Him belongs the dominion, and to Him belongs the praise, and He is capable of all things' (La ilaha illallah, wahdahu la sharika lah, lahul-mulku wa lahul-hamdu, wa huwa 'ala kulli shay'in qadir) ten times, it shall be equivalent to the freeing of four slaves, and ten good deeds shall be written for him because of them, and ten evil deeds shall be erased from him because of them, and ten degrees shall be raised for him because of them. And they shall be a protection for him from the Shaytan until he reaches the evening. And if he says it after the sunset prayer, it shall be the same as that."