As the angels, O Savior, wondered at Thy strange elevation, and the Disciples were amazed at Thy dread rising, Thou didst ascend in glory, being God, and the gates were lifted up for Thee. Wherefore, the heavenly powers were surprised, shouting, Glory to Thy condescension, O Savior; glory to Thy reign; glory to Thine Ascension, O Thou Who alone art the Lover of mankind.
--Orthros of the Feast
On the fortieth day after Jesus was resurrected from the dead, He was taken up into the heavens in a cloud.
"The cloud which today envelopes Jesus and ascends with him to heaven represents the smoke of the sacrifice rising from the altar to God. The sacrifice is accepted, and the victim is admitted to God's presence where it will continue to be offered in an eternal and heavenly manner. The work of our salvation has been accomplished and is blessed."
From The Year of the Grace of the Lord