The phrase 'the first day of the week' has several applications. The first day of the week means it is a new beginning, a starting point of something.
First, it was the very first time, the first day of the week, the Risen Lord appeared to His apostles, who were in hiding behind the closed doors. Jesus was buried behind the 'door' of the tomb, and that door was wide open; it was rolled to one side. Jesus met His apostles to open His apostles' eyes, to open their minds to recall what Jesus had prophesized about this amazing encounter Mk 14,28. We say when one door closes; other door opens. By human freewill, sin crept in our lives, and that opened the door of hell. The resurrection of Christ opened the door of God's kingdom for all Jesus' followers. In the creation account, God separated light from darkness Gn.1:1. In the resurrection account, Christ's light shone through darkness on the first day of the week. Christ offered the new light, and restored God's peace. Twice Christ greeted His apostles: 'Peace be with you' v.20.
Second, after the Last Supper, Jesus' apostles lived in fear. Meeting the Risen Lord, their hearts filled with joy. The Risen Christ restored their shattered lives, brightened their future, reinstated their hope. They began to live new life in Christ.
Third, on the first day of the week, Christ showed the apostles His wounds. Just after three days, the wounds on His hands and His side had not been healed. These unhealed wounds confirmed the Christ they met now was the same Christ as before the crucifixion. It also meant Christ had a special love for His apostles, and showed great concern for their well- being.
Fourth, the first day of the week was also the first day Christ's apostles received the new mission: 'As the Father sent me, so am I sending you'. v.21. Christ gave the apostles the same mission He had received from the Father. From then on they spread the Good News to all corners of the earth.
Fifth, the first day of the week marked the day the apostles received Christ's Spirit, when He breathed on them, saying: 'Receive the Holy Spirit'. v.22. What Jesus promised them was fulfilled. The Spirit of the Risen Lord would accompany the apostles throughout their lives in the mission fields.
Sixth, the first day of the week marked the beginning of the apostles' new life. They were in hiding, running away. They were like the lost sheep; scattered. The Risen Christ looked for them, gathered them back. The apostles were given the power to proclaim the message of forgiveness, that Christ has gained for those who repent, starting with the thief on the cross.
Seventh, the other apostles had seen the Risen Christ on the first day of the week, but on that day Thomas was missing. This was the very first time for Thomas to see the Risen Christ, and he made a public confession: 'My Lord, and my God'. v.28. This echoed what the centurion confessed under the foot of the cross: 'Truly, this man was the Son of God' Lk 23,48. Again, this confession reconfirmed the crucified Christ and the Risen Christ as One and the same Person.
We pray to have some share of the joy Jesus' apostles had when they first met the Risen Lord.