On July 12, Orthodox believers mark one of their great holidays -- Day of Holy Glorious and Most Laudable First Supreme Apostles Peter and Paul. They more than other apostles had done to preach Christianity among Israelites and pagans, and for that reason the Church calls them first supreme apostles.
By Gospel tradition, Jesus Christ himself summoned fisherman Simon /Peter/ and his brother Andrew to be his pupils. Simon became the most zealous follower of Christ and for his strong faith that Jesus was Christ the Son of God, he was named by him as Peter, which means "stone". As Gospel from Matthew says, the Saviour promised to base his church on this stone. Peter was the first to start preaching in Jerusalem about the resurrected Christ and suffered a lot for his faith.
Paul had previously had the name of Saul and was a harsh persecutor of Christians. He even took part in murdering the first Christian martyr Archdeacon Stephanos, but was miraculously converted to the faith by God himself. The Acts of Apostles say that on his way to Damascus Saul suddenly heard a voice calling to him from the skies: "Saul, why do you persecute me?" "Who art thou, Master?" Saul asked in horror and heard in reply: "I am Jesus, it is him that you are chasing". After that Saul obeyed God, was baptised, given the name of Paul and became a zealous preacher of Christianity. After making several voyages across the Mediterranean, he founded churches in Asia Minor, Greece and Rome.
In 67 in Rome, during a savage pursuit of Christians on the part of Emperor Nero, Apostle Peter was crucified head down on a cross, and Apostle Paul beheaded by a sword.
On Peter and Paul Day, Orthodox Christians complete Peter's fast instituted by the Church in memory of the services and sufferings of the holy apostles.