Musannaf Ibn Abi Shayba 33:838

Ibn Fudayl narrated to us, from Layth, from Talha, from Abd al-Rahman ibn Awsaja, from al-Bara’, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever says: '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,' it is like the freeing of a slave."