The commissioning of the apostles and the promise to them of the power of the Spirit is the last utterance of Jesus on earth. Luke pictures his exaltation as a physical event, comparable with the ascension of Elijah. The disciples of Jesus similarly look on as he is taken, and they receive the Spirit from him at Pentecost. They are witnesses of his glorification as well as of his earthly life and his resurrection. The cloud is a sign of the divine presence as at the Transfiguration.
White robes are the symbol of a heavenly being.
The angelic messengers explain the meaning of the departure of Jesus. He is now exalted in glory and will not again be seen in his own person, except in extraordinary revelations, until the Second Coming. Meanwhile the apostles are to move on to their task of administering his kingdom on earth by proclaiming the gospel of which they are the commissioned witnesses, united to the ascended Jesus by the promised Spirit. The earthly life of Jesus is now at an end and he is to be known in a new mode until the Second Coming when he will come as the Son of Man in a cloud with power and great glory. This will not be soon, so the apostles are not to stand looking into heaven but are to move on in faith.