But 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 Judaea, and in Samaria, and unto the uttermost part of the earth. But ye shall receive power - Ληψεσθε δυναμιν. Translating different terms of the original by the same English word is a source of misapprehension and error. We must not understand δυναμις which we translate power in this verse, as we do εξουσια, translated by the same word in the preceding verse. In the one, God's infinite authority over all times and seasons, and his uncompellable liberty of acting or not acting in any given case, are particularly pointed out: in the other, the energy communicated by him to his disciples, through which they were enabled to work miracles, is particularly intended; and δυναμις, in general, signifies such power, and is sometimes put for that of which it is the cause, viz. a miracle. See Matthew 7:22; Matthew 11:20-23; Matthew 13:54, Matthew 13:58; Mark 6:5; Luke 10:13; and Acts 2:22. The disciples were to be made instruments in the establishment of the kingdom of Christ; but this must be by the energy of the Holy Ghost sent down from heaven; nevertheless, this energy would be given in such times and seasons, and in such measures, as should appear best to the infinite wisdom of God. Christ does not immediately answer the question of the disciples, as it was a point savouring too much of mere curiosity; but he gave them such information as was calculated to bring both their faith and hope into action. St. Chrysostom has well observed, "that it is the prerogative of an instructer to teach his disciple, not what he wishes to learn, but what his master sees best for him:" Διδασκαλου τουτο εστι μη ἁ βουλεται ὁ μαθητης, αλλ' ἁ συμφερει μαθειν, διδασκειν.
Ye shall be witnesses - in all Judea, etc. - Though the word earth, ἡ γη, is often used to denote Judea alone, yet here, it is probable, it is to be taken in its largest extent. All the inhabitants of the globe might at that period be considered divisible into three classes.
1. The Jews, who adhered to the law of Moses, and the prophetic writings, worshipping the true God only, and keeping up the temple service, as prescribed in their law.
2. The Samaritans, a mongrel people, who worshipped the God of Israel in connection with other gods, 2 Kings 17:5, etc., and who had no kind of religious connection with the Jews. See on Matthew 10:5 (note). And,
3. The Gentiles, the heathens through all other parts of the world, who were addicted to idolatry alone, and had no knowledge of the true God.
By the terms in the text we may see the extent to which this commission of instruction and salvation was designed to reach: to the Jews; to the Samaritans, and the uttermost part of the earth, i.e. to the Gentile nations, thus, to the whole human race the Gospel of the kingdom was to be proclaimed. When the twelve disciples were sent out to preach, Matthew 10:5, their commission was very limited - they were not to go in the way of the Gentiles, nor enter into any city of the Samaritans, but preach the Gospel to the lost sheep of the house of Israel: but here their commission is enlarged, for they are to go into all the world, and preach the Gospel to every creature. See Matthew 28:18.