Musnad Ahmad 30:180

Sufyan narrated to us, from Abu al-Zinad, from al-A’raj, from Abu Hurayrah, attributing it to the Prophet (may Allah bless him and grant him peace), who said: "Allah, the Mighty and Majestic, says: 'O son of Adam, spend, and I shall spend upon you.'" And he said: "The Right Hand of Allah is full, overflowing, and nothing diminishes it, neither night nor day."