Acts 1:3 . . . to whom He also presented Himself alive after His suffering by many infallible proofs, being seen by them during forty days and speaking of the things pertaining to the kingdom of God.
Acts 1:8 "But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth."
In Acts we read how Peter, John and the other disciples displayed great courage and boldness when they proclaimed the Gospel, when they stood before the Sanhedrin, when they endured beatings. What accounts for this? When we read the Gospels, right after Gethsemane and the Lord's death these men were so terrified that they went into hiding. Peter was also frightened and denied the Lord 3 times.
Acts 1 helps to explain the transformation. First, we read that the Lord gave them infallible evidence that He had really risen from the dead. He was no ghost or phantom. He had risen bodily from the grave for them to see, hear, and touch. They witnessed the Lord's eating food, suddenly appearing out of nowhere, and conversing with them personally. All the things Jesus had said to them earlier started to make sense.
Second, the Lord gave them teaching concerning the kingdom of God for forty days. What a class! This formed the basis for the "apostles doctrine" in Acts 2 and elsewhere. Seeing the risen Christ talking about the eternal kingdom of God with His disciples left an indelible imprint on them.
Third, they were about to receive the Holy Spirit. Jesus told them that when He comes, they would receive Divine power, not from the outside but within them. The Holy Spirit would be with them and dwell in their very persons to provide them wisdom, strength, courage, and boldness.
This helps to explain the incredible success and growth of the early church, for in just a few short years the news of the kingdom of God had spread from Jerusalem all the way to Rome! This is nothing less than divine enabling!
Later in history, we discover that all of the Lord's 12 disciples, including Paul, underwent martyrdom with the exception of John who suffered terribly in other ways. They were willing to suffer and die for these unshakeable truths, knowing their ultimate destiny.
May we reflect upon these three powerful reasons for the disciples courage, and then invite the Lord to do the same for us!