12 “‘Observe the Sabbath day, to keep it holy, as the Lord your God commanded you. 13 Six days you shall labor and do all your work, 14 but the seventh day is a Sabbath to the Lord your God. On it you shall not do any work, you or your son or your daughter or your male servant or your female servant, or your ox or your donkey or any of your livestock, or the sojourner who is within your gates, that your male servant and your female servant may rest as well as you. 15 You shall remember that you were a slave in the land of Egypt, and the Lord your God brought you out from there with a mighty hand and an outstretched arm. Therefore the Lord your God commanded you to keep the Sabbath day.
In modern times this has come to mean "Go to church on Sunday." A lot of Christians aren't descended from the 12 tribes of Israel, however, very clearly requires us to use it as a day of rememberence for bringing us our of our own personal Egypt. Moreover, Paul wrote:
5 One person esteems one day as better than another, while another esteems all days alike. Each one should be fully convinced in his own mind. 6 The one who observes the day, observes it in honor of the Lord. The one who eats, eats in honor of the Lord, since he gives thanks to God, while the one who abstains, abstains in honor of the Lord and gives thanks to God. 7 For none of us lives to himself, and none of us dies to himself. 8 For if we live, we live to the Lord, and if we die, we die to the Lord. So then, whether we live or whether we die, we are the Lord’s. 9For to this end Christ died and lived again, that he might be Lord both of the dead and of the living.
Which reminds us that the important part is to remember God in all we do, and honor him everyday.