11 In my first book I told you, Theophilus, about everything Jesus began to do and teach 2 until the day he was taken up to heaven after giving his chosen apostles further instructions through the Holy Spirit. 3 During the forty days after he suffered and died, he appeared to the apostles from time to time, and he proved to them in many ways that he was actually alive. And he talked to them about the Kingdom of God.
Matthew Henry's Commentary on Acts 1:1-3
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.