Musnad Ahmad 30:3688

Muhammad ibn Ubayd and Abu Ubaydah narrated to us, from Muhammad ibn Amr, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) said: "Allah, the Almighty and Majestic, says: 'And who is more unjust than one who attempts to create like My creation? Let them create a gnat, and let them create an atom.'" Abu Ubaydah said: "Let them create."