Muhammad’s ascension to see God face-to-face is as key to understanding Islam as Jesus’ crucifixion and resurrection are to Christians, or Prince Siddhartha achieving enlightenment by sitting under the Bodhi tree. The narrative of the Ascension is that the archangel Gabriel awakened Muhammad from sleep in the middle of the night in Mecca, and then took him to Jerusalem, whereupon they ascended to Heaven. They rose level by level through the levels and layers of Paradise, where they met with the previous prophets including Abraham, Moses, and Jesus. Ultimately, Gabriel brought Muhammad to the very threshold of Divine presence. There, the archangel came to a sudden and abrupt stop, refusing to go any further. Gabriel then lowered his wings to put the Prophet on the ground.
Muhammad, somewhat puzzled, asked Gabriel: “Friend, you have been such a faithful companion from Mecca to Jerusalem to Heaven. Why do you stop here, and so suddenly?” Read more here.