Musnad Ahmad 30:3629

'Abd al-Samad narrated to us, Sulayman—meaning Ibn al-Mughirah—narrated to us, from 'Ali ibn Zayd, from Abu 'Uthman, who said: It reached me from Abu Hurayrah that he said: It reached me that Allah, the Mighty and Majestic, gives His believing servant for a single good deed one million good deeds. He said: It was decreed that I set out for Hajj or 'Umrah, so I met him and said: A hadith reached me from you that you say: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Indeed, Allah, the Mighty and Majestic, gives His believing servant for a good deed one million good deeds?" Abu Hurayrah said: No, rather I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Indeed, Allah, the Mighty and Majestic, gives him two million good deeds." Then he recited: {He multiplies it and gives from Himself a great reward} [An-Nisa: 40]. He then said: When He says: {A great reward} [An-Nisa: 40], then who can estimate its measure?