30 Apr. The believers choose a new 12th apostle
"During this time [between Ascension Day on Thursday18th May 30AD and the Day of Pentecost on Sunday 28th May 30AD] there was a meeting of the believers (about 120 of them)."
"Peter stood up and said, 'Brothers and sisters, in the [Jewish] Scriptures the Holy Spirit said through David something that must happen involving Judas... In the Book of Psalms, this is written: "May his place be empty; leave no one to live in it." [Psalm 69:25] And it is also written, "Let another man replace him as leader."'" [Psalm 109:8]
"So now a man must become a witness with us of Jesus' being raised from the dead. He must be one of the men who were part of our group during all the time the Lord Jesus was among us - from the time John was baptising people until the day Jesus was taken up from us to heaven."
"They put the names of two men before the group. One was Joseph Barsabbas, who was also called [Joseph] Justus. The other was Matthias. The apostles prayed, 'Lord, you know the thoughts of everyone. Show us which one of these two you have chosen to do this work'..."
"Then they used lots to choose between them, and the lots showed that Matthias was the one. So he became an apostle with the other eleven."
(Acts 1:15-26)
After the death and resurrection of Jesus, and his return to his heavenly Father, Jesus's followers stayed in Jerusalem and met together regularly in the large upper room (the guest room) at John Mark's house "where they were staying" (see Acts 1:13 & 12:12).
The remaining eleven disciples prayed together with some of the women followers and Jesus's close family. They discussed whether they should remain as a group of 11 followers, or whether they should appoint a 12th disciple to take the place of Judas, who had committed suicide when he realised that his betrayal of Jesus would lead to his death (see Acts 1:16-19).
During his early ministry, Jesus had deliberately chosen 12 followers (called 'apostles') to be his close circle of friends and evangelists (see Matthew 10:1-6). These 12 followers were sent out specifically to preach the Good News of the arrival of the "kingdom of heaven" to the 12 tribes of Israel descended from the12 sons of Jacob (who was given the name 'Israel') (see Genesis 35:9-12 & 22-26, and Joshua 14:2-5). Jesus told them, "Don't go to the non-Jewish people or to any towns where the Samaritans live. But go to the people of Israel, who are like lost sheep." (Matthew 10:5-7)
After the death of Judas, the 11 apostles could have carried on without appointing another close follower to their group; but they decided to ask a 12th disciple to join them as Jesus had appointed 12 close followers for a symbolic reason. The 12 apostles were to witness to the 12 tribes of Israel - symbolising the WHOLE of the Jewish nation. (Matthew 10:5)
As a result, they drew up a short list of two suitable candidates, and chose Matthias by casting lots, in the same way that the land of Canaan had been divided amongst the 12 tribes of 'Israel' (see Joshua 14;2), and so that God, rather than any mere man, was seen to be responsible for appointing Judas's replacement.
With the apostles back to their full complement of twelve, they were nearly ready to launch their mission to the 12 tribes of Israel; but not until they received a double-dose of God's Holy Spirit to empower them for action!
The map shows the places where Jesus's close circle of friends came from.
You can read more about the background of the 12 apostles (and some other close friends of Jesus) @ https://www.thebiblejourney.org/…/who-were-jesuss-followers/