Al-Sha'bi narrates: We were with al-Rabi' bin Khuthaym, and that day he narrated: "Whoever says these words: 'There is no true god but Allah, alone, without partner; His is the dominion and to Him belongs all praise; He gives life and causes death, and He has power over all things,' once or ten times, it will be for him equal to freeing one slave or ten slaves." I asked: From whom did you hear this? He said: From Abdur-Rahman bin Abi Layla. So I went to him and he narrated this hadith. I asked: From whom did you hear this? He said: From Abu Ayyub, who narrated it from the Prophet (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4003