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.

1. Presented himself alive - His resurrection was not a secret event. His resurrection was witnessed by many people, in addition to the apostles.

2. After his passion (KJV) - He was seen alive, walking, talking, after His suffering. The term "passion" is used to include the trial, cruel death AND triumphant resurrection.

3. 40 days - There are 50 days between Passover and Pentecost. Jesus was with his apostles for 40 days - leaving only 10 days until Pentecost.

4. Kingdom of God - The apostles still did not understand the nature of Christ's Kingdom. They are still thinking about a physical kingdom, one that would overthrow the Romans and return control to the Jews.