Acts 1:8

Wherefore He saith, "Ye shall receive power, after that the Holy Ghost is come upon you, and ye shall be My witnesses both in Jerusalem, and in all Judaea." And witnesses they became by means of miracles, for unspeakable is the grace of the Spirit and multiform the gift. But this comes to pass, that thou mayest learn that the gift and the power of the Father, the Son, and the Holy Ghost, is One. For things which appear to be peculiar to the Father, these are seen also to belong to the Son, and to the Holy Ghost. "How then," saith some one, "doth none come to the Son, `except the Father draw him'?" Why, this very thing is shown to belong to the Son also. "I," He saith, "am the Way: no man cometh unto the Father but by Me." And observe that it belongeth to the Spirit also; for "No man can call Jesus Christ Lord, but by the Holy Ghost." Again, we see that the Apostles were given to the Church at one time by the Father, at another by the Son, at another by the Holy Ghost, and that the "diversities of gifts" belong to the Father, the Son, and the Holy Ghost.

"But ye shall receive power, after that the Holy Ghost is come upon you." As in the former instance He had not answered their question (for it is the part of a teacher to teach not what the disciple chooses, but what is expedient for him to learn), so in this, He tells them beforehand, for this reason, what they ought to know, that they may not be troubled. In truth, they were yet weak. But to inspire them with confidence, He raised up their souls, and concealed what was grievous. Since he was about to leave them very shortly, therefore in this discourse He says nothing painful. But how? He extols as great the things which would be painful: all but saying, "Fear not: for ye shall receive power, after that the Holy Ghost is come upon you; and ye shall be witnesses unto Me both in Jerusalem, and in all Judea, and in Samaria." For since he had said, "Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not" (Matt. x. 5), what there He left unsaid, He here adds "And to the uttermost part of the earth;" and having spoken this, which was more fearful than all the rest, then that they may not again question Him, He held His peace.

"Ye shall receive power," says He, "when the Holy Ghost is come upon you." "Is come upon you," not, "is sent," to show the Spirit's coequal Majesty. "And ye shall be witnesses to Me." He hinted at the Ascension.