11 Dear Theophilus, in the first volume of this book I wrote on everything that Jesus began to do and teach 2 until the day he said good-bye to the apostles, the ones he had chosen through the Holy Spirit, and was taken up to heaven. 3 After his death, he presented himself alive to them in many different settings over a period of forty days. In face-to-face meetings, he talked to them about things concerning 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.