What does Mark 13:3 mean?

The Mount of Olives is a hill to the east of Jerusalem. On its eastern flank is the town of Bethany where Jesus' friends Mary, Martha, and Lazarus live. Since Jesus and the disciples arrived in the area, they have spent nights on the Mount of Olives and days in the temple courtyard where Jesus has been teaching (Luke 21:37).

From the Mount of Olives, the disciples can look across the Kidron Valley, through the Eastern Gate, straight to the front wall of the temple. In AD 810, the gate was closed by Muslims, only to be reopened three hundred years later by the Crusaders. In 1541, Ottoman Sultan Suleiman bricked it in closed, either for defense or in an attempt to thwart the prophecy that Jesus will use it when He returns. In 2019, it remains closed.

The four disciples listed are the first four Jesus formally invited to follow Him (Mark 1:16–20). Peter, James, and John have been Jesus' closest friends since the beginning of His public ministry. They were the only three to watch Jesus raise Jairus' daughter from the dead (Mark 5:37–42) and witness the Transfiguration (Mark 9:2–13). Soon, Jesus will ask the three to pray in the garden of Gethsemane (Mark 14:32–42). In this case, Peter's brother Andrew has come as well.