Bear this in mind that while the Sabbath day is the seventh day of the week, the rest, which the Sabbath day brings to view, is continuous. Only those who rest in the Lord all the time keep the Sabbath. When Jesus cried, “It is finished,” He was announcing that through His cross could be obtained the perfect works of God, which were finished from the foundation of the world.
God has rested upon the seventh day, and has blessed and sanctified it. He calls it His Sabbath, and tells us to keep it holy.
Can we obey Him by selecting some other day, and say that it makes no difference, provided we keep one whole day out of the seven?
So it is that the Gospel has to do with eternal things, but eternal things in the present time. The trouble with people is that they regard eternity as only future, whereas eternity is past, present, and future. It has been, is, and is to be.