Acts 1:3

1:3 To the same apostles also, after his suffering, he presented himself alive with many convincing proofs. He was seen by them over a forty-day period and spoke about matters concerning the kingdom of God.

Acts 1:8

1:8 But you will receive power when the Holy Spirit has come upon you, and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the farthest parts of the earth.”

Acts 1:21-22

1:21 Thus one of the men who have accompanied us during all the time the Lord Jesus associated with us, 1:22 beginning from his baptism by John until the day he was taken up from us – one of these must become a witness of his resurrection together with us.”