Sunan At-Tirmidhi

Ubadah bin As-Samit narrated that the Messenger of Allah (s.a.w) said:""In Paradise, there are a hundred levels, what is between every two levels is like what is between the heavens and the earth. Al-Firdaus is ts highest level, and from it the four rivers of Paradise are made to flow forth. So when you ask Allah, ask Him for Al-Firdaus."" Another chain reports a similar narration