11 I composed the first discourse, O Theophilus, concerning all things which Jesus began both to do and to teach, 2 until that day in which, having by the Holy Spirit charged the apostles whom he had chosen, he was taken up; 3 to whom also he presented himself living, after he had suffered, with many proofs; being seen by them during forty days, and speaking of the things which concern the kingdom of God; 4 and, being assembled with [them], commanded them not to depart from Jerusalem, but to await the promise of the Father, which [said he] ye have heard of me. 5 For John indeed baptised with water, but ye shall be baptised with the Holy Spirit after now not many days.
Matthew Henry's Commentary on Acts 1:1-5
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.