Acts 1:3-4

³And to whom he gave clear and certain signs that he was living, after his death; for he was seen by them for forty days, and gave them teaching about the kingdom of God:

⁴And 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: