Acts 1:3

3 After his suffering, he presented himself to them and gave many convincing proofs that he was alive. He appeared to them over a period of forty days and spoke about the kingdom of God.

Read Acts 1:3 Using Other Translations

To whom also he shewed himself alive after his passion by many infallible proofs, being seen of them forty days, and speaking of the things pertaining to the kingdom of God:
He presented himself alive to them after his suffering by many proofs, appearing to them during forty days and speaking about the kingdom of God.
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.