Chapter 24 of the gospel of St. Luke relates the Resurrection of Jesus from the dead after His crucifixion.  On the third day after Jesus's death, Peter ran to the tomb and found his Lord gone.  As Peter talks to others and walks with them, Jesus appears beside them without their recognition. However, after Jesus takes bread with them, the others recognize the Lord, but he disappears.

The people with Simon Peter return to Jerusalem where they encounter the other apostles. As the people talk to the eleven apostles, Jesus again appears, telling them not to be afraid. Then,

He opened their minds, that they might understand the Scriptures.

In verses 46-49, Jesus instructs his followers that they should preach in His name about His death and resurrection to all nations, starting with Jerusalem. But, first Jesus wants the people to wait (tarry) in the city of Jerusalem where they will receive "power from on high"; that is, they will receive the power of the Holy Spirit and inspiration to preach.