Musnad Ahmad 30:1354

Fazara ibn Amr narrated to us, Fulayh informed me, from Hilal ibn Ali, from Abd al-Rahman ibn Abi Amra, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever believes in Allah and His Messenger, establishes prayer, and fasts Ramadan, it is a right upon Allah the Almighty and Majestic to admit him into Paradise, whether he migrated in the cause of Allah or remained in the land in which he was born." They said: "O Messenger of Allah, shall we not inform the people of that?" He said: "Indeed, in Paradise there are one hundred levels; the highest of them is for the mujahideen in His cause. The distance between every two levels is like the distance between the heaven and the earth. So when you ask Allah the Almighty and Majestic, ask Him for al-Firdaws, for it is the middle of Paradise and the highest of Paradise, and above it is the Throne of the Most Merciful, the Almighty and Majestic, and from it gush forth the rivers of Paradise."