4 And when they were all together, with him, he gave them orders not to go away from Jerusalem, but to keep there, waiting till the word of the Father was put into effect, of which, he said, I have given you knowledge: 5 For the baptism of John was with water, but you will have baptism with the Holy Spirit, after a little time.
Matthew Henry's Commentary on Acts 1:4-5
Commentary on Acts 1:1-5
(Read Acts 1:1-5)
Our Lord told the disciples the work they were to do. The apostles met together at Jerusalem; Christ having ordered them not to depart thence, but to wait for the pouring out of the Holy Spirit. This would be a baptism by the Holy Ghost, giving them power to work miracles, and enlightening and sanctifying their souls. This confirms the Divine promise, and encourages us to depend upon it, that we have heard it from Christ; for in Him all the promises of God are yea and amen.