Luke 24:49

And behold, I send the promise of My Father upon you, i.e., after a few days, when the Feast of Pentecost is come, I will send you the Holy Spirit, who will teach you clearly many things besides these, and enable you to preach the gospel to all nations.

But tarry ye in the city of Jerusalem until ye be endued with power from on high. δυνάμιν, i.e., with the gifts of the Holy Spirit, for "as a general does not permit his soldiers who are about to meet a large number, to go out until they are armed, so also the Lord did not permit His disciples to go forth to the conflict before the descent of the Spirit." S. Chrysostom in Catena.

Tropologically. S. Gregory (Past. iii 26) says, "We abide in a city when we keep ourselves close within the gates of our minds, lest by speaking we wander beyong them; that when we are perfectly endued with divine power we may then as it were go out beyond ourselves to instruct others."

Ver. 50. And He led them out as far as to Bethany, and from thence to the mount of Olives. Bethany was about fifteen furlongs [stadia] from Jerusalem, and close by the mount of Olives. Christ went to Bethany to say farewell to Lazarus and his sister, and to bring them with Him to mount Olivet, in order that they might witness His ascension, and share in His triumph.

And He lifted up his hands towards heaven, as if seeking a special blessing for his disciples.

And blessed them, signing them with the sign of the Cross, as Dionysius the Carthusian and others think. Indeed, S. Jerome, commenting on the words, "I will set a sign upon them," Isaiah 65:19, says, Our ascending Lord left us this sign, or rather placed it on our foreheads, so that we may freely say, "The light of Thy countenance is lifted up upon us, O Lord." For the Cross is the sign of Christ, which is the fountain of all benediction and grace. Hence the tradition which has come down from the time of Christ and the Apostles that in giving a blessing the hands should always form the sign of the Cross.

Therefore, says Theophylact, we should learn when about to leave our dependents or friends, to give them our blessing, and, signing them with the sigh of the Cross, commit them to the keeping of God.