`Who is there?' He replied: `Jibril.' He was asked: `Who is with you?' He said: `Muhammad.' Then he ascended to the second heaven and requested for the opening of the gate. He was asked: `Who is there?' He said: `Jibril.' He was asked: `Who is with you?' He replied: `Muhammad.' In the same way he ascended to the third, fourth and all the heavens (i.e., until the seventh). At all of the gates he was asked: `Who is there?' He replied: Jibril.'''

[Al-Bukhari and Muslim].