In the Old Testament, the people of God recognized Saturday as the holy day of rest. From sundown on Friday to sundown on Saturday, God’s followers refrained from working. Their express intent was to follow the example of God Himself, who created for six days and then rested on the seventh. This day gave them the opportunity to reflect on God, focus on family, and get recharged both physically and spiritually.
But about 2,000 years ago, there was a radical shift among the people of God. They moved their day of worship from Saturday to Sunday because of one monumental and life-giving event: the resurrection of Jesus Christ. It all started around AD 33. The week began like any other week. Jesus came into Jerusalem riding on a young donkey on Sunday. A large crowd welcomed Him with praises and honor, for they believed that He had come to deliver them from the oppression and suffering they faced (Matthew 21:11).
Jesus went to the temple on Monday and addressed the corruption He saw. He overturned the tables of the moneychangers because of the corruption He saw (Matthew 21:12-22). 
All the animals throughout the generations had pointed to the coming Messiah, the perfect sacrificial Lamb. Jesus was that perfect Sacrifice. His death was near, and His work would be permanent. God’s people no longer needed to make temporary sacrifices. Their Savior had come.
On Tuesday, He confronted the Pharisees about their unrighteous hearts, went to the Mount of Olives, and gave the Olivet Discourse. There, Jesus revealed some of the future events that awaited His followers. He talked about His return and the final judgment that everyone would face (Matthew 21:23-24:51).
Scripture doesn’t record what happened on Wednesday of that week. But on Thursday, Jesus gathered with His disciples to prepare and eat the Passover meal. He washed their feet and established the Lord’s Supper as He foretold of His death. That evening, He left for the Garden of Gethsemane and prayed to the Father about the coming events. He submitted to the will and plan of the Father, though He knew it came at a high cost. Then, Judas Iscariot betrayed Him, and He was placed under arrest by the Sanhedrin (Matthew 26:17-75).
On Friday, Jesus was sentenced to death, though He had committed no wrong. The Romans beat Him, and He faced a brutal crucifixion and death. He had been beaten so badly that He was unrecognizable as a man. That evening, His followers prepared His body for burial. And they laid Him in the tomb (Matthew 27:1-62). 
Jesus’ followers mourned His death on Saturday. After sundown, they ceremonially treated Jesus’ body for burial (John 19:39-40). They and the rest of God’s people had continued their practice of resting and worshipping that Sabbath day (Matthew 27:62-66). This was the last time that the followers of God would come together as a universal whole to do this.
The events of the next day changed the course of history forever. Several women went to the tomb early on Sunday morning, only to find that Jesus was no longer there (Matthew 28:1-13). They ran to tell the other disciples and soon discovered that He had risen from the dead. He had successfully paid the debt of sin and provided reconciliation with the Father.
That evening, Jesus appeared to the disciples, who had gathered together in an upper room to pray. They were beginning to understand that Jesus had come not to bring about political change but to usher in a New Covenant. He had come to fulfill the Law, and His Sacrifice broke down the barriers between Jews and Gentiles. The people of God no longer had to live according to laws that set them apart from the nations because the nations were invited to come to Jesus as they were for salvation.
One of these laws that served to distinguish Israel from the nations was the law of the Sabbath. Jesus’ resurrection from the dead changed the way the people of God approached this command. Rather than resting on a specific day with oftentimes legalistic measures, they began to understand that Jesus was their ultimate rest.
From then on, the early church gathered together on Sundays. They partook of the Lord’s Supper as Jesus had instructed, worshipping Him as the true and living Messiah and remembering the Sacrifice that He had made on their behalf. They came together to celebrate the fact that Jesus had defeated death and attained victory over sin. In Acts 20, we learn that these gatherings on Sundays began to include teaching from the Word and praises as well. 
This practice has been carried on throughout the generations so that Christians two millennia removed from these events continue to gather to worship on Sundays. Some inquiring minds might ask why the life of one man is celebrated with such fervor and dedication. After all, Scripture is clear that Jesus wasn’t even the only One to rise from the dead that day. Matthew 27:52-53 says, “The tombs were also opened. And many bodies of the saints who had fallen asleep were raised, and coming out of the tombs after his resurrection they went into the holy city and appeared to many.”
But Jesus wasn’t just any man. He was the God-Man. The Bible explains that all of humanity had rebelled against God and were deserving of death. They had all committed sin and were undeserving of being in the holy presence of God. They could no longer make themselves perfect, and they had no hope of saving themselves.
But God sent His Son to live the perfect life that we could not live. When He died, He took the punishment for our sins that we deserved. And if we repent from our sins and believe in Him, He grants to us His righteousness. When God looks upon Christians, He sees Jesus’ perfection. Jesus came to give us salvation. He alone is the way that leads to the Father. And that is worth celebrating, indeed!