Acts 1:8

But ye shall receive power
From on high, with which they were to be endured, ( Luke 24:49 ) meaning the power of the Holy Ghost, strength from him to preach the Gospel, and work miracles in confirmation of it, and courage and greatness of mind, amidst all reproaches and persecutions, to face and oppose their enemies, profess the name of Christ, abide by his truths and ordinances, make their way through all opposition and difficulties, and spread the Gospel all over the world; for intend of enjoying worldly ease, honour, wealth, and riches, they were looking for, our Lord gives them to understand that they must expect labour, service, afflictions, and trials, which would require power and strength, and which they should have:

after that the Holy Ghost shall come upon you;
from above, from heaven, as he did, and sat upon them in the form of cloven tongues, and of fire; upon which they were filled with knowledge and zeal, with strength and courage, and with all gifts and abilities necessary for their work:

and ye shall be witnesses unto me;
of the person of Christ, of his deity and sonship, of his incarnation, his ministry, and his miracles, of his suffering and death, of his resurrection from the dead, and his ascension to heaven. This was to be their work, and what belong to them, and not to enquire about a temporal kingdom, and the setting up of that, and the times and seasons of it; their business was to testify of the sufferings of Christ, and the glory that followed, and to preach a crucified Jesus, as the only Saviour of lost sinners: and this

both in Jerusalem,
the "metropolis" of the nation, and there, in the first place, where such dwelt who had been concerned in the crucifixion of Christ, many of whom were to be called by grace, and converted through their ministry:

and in all Judea;
that part of the land of Israel which was distinct from Samaria and Galilee, and from beyond Jordan; where churches were to be planted, as afterwards they were; see ( Acts 9:31 ) .

And in Samaria;
where Christ had before forbid his disciples to go; but now their commission is enlarged, and they are sent there; and here Philip went upon the persecution raised against the church at Jerusalem, and preached Christ with great success, to the conversion of many; and hither Peter and John went to lay their hands on them, and confirm them; see ( Acts 8:5 Acts 8:14 )

and unto the uttermost part of the earth;
throughout the whole world, whither the sound of the apostles, and their words went, ( Romans 10:18 ) .