There is no requirement in the bible about not working on Sunday. I think what the OP was talking about was this passage:
"On six days work may be done, but the seventh day shall be holy to you as the sabbath of complete rest to the LORD. Anyone who does work on that day shall be put to death. "
This is talking about the Jewish Sabbath and this day is on Saturday.
The other thing is that this is part of the many Jewish laws under the old covenant.
In Christ, we are under a new covenant. And, under the new covenant the various ceremonial laws have been fulfilled in Christ. Since they were a foreshadowing of Christ. But, once Christ came they were no longer necessary. Instead, under the new covenant we have baptism instead of circumcision. Baptism brings us into the Body of Christ. When we are baptized into Christ we die to the law and are no longer under the law.
Rom 3:28 - we are justified by faith and not by works of the law.
Rom 6:4 - we were baptized into Christ’s death
Rom 7:1 - the law only has jurisdiction over someone who is alive
Rom 7:4 - we have been put to death to the law through the body of Christ
Jesus said he did not come to bring us condemnation but rather eternal life for all who believe in him. It was also a law that adulterers be stoned but when they brought the woman who had been caught in adultery to Jesus he did not stone her but had mercy on her and told her to sin no more. Jesus sets the example for Christians to follow. He commands us to forgive others so that we can be forgiven. He commands us to be merciful as he has been merciful towards us. Jesus dying on the cross is an expiation of our sins which opens a new door of grace and mercy for us not found under the old covenant restrictions.
The Old Covenant was under law. The New Covenant is under grace.
The Catholic Church teaches that we should observe a day of rest on Sunday, not working unnecessarily, if possible. In this we keep the spiritual sense of the Sabbath, that is a day of rest and worship of the Lord. Rest from labor and worship by attending Mass. Even though we are no longer bound to practice the Jewish Sabbath as the Sabbath is fulfilled in Christ since man enters God’s eternal rest through Christ, we still honor the teaching of the Church which elaborates God’s will for us to have a day of rest for leisure, family, and worship.