Oneness, Uniqueness of Allah (Tawheed)

Bukhari :: Book 9 :: Volume 93 :: Hadith 477

Narrated Masruq:

'Aisha said, "If anyone tells you that Muhammad has seen his Lord, he is a liar, for Allah says: 'No vision can grasp Him.' (6.103) And if anyone tells you that Muhammad has seen the Unseen, he is a liar, for Allah says: "None has the knowledge of the Unseen but Allah."