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.
We are reconciled to God by the death of Christ, and saved by His life. The life, which does this, is the life from which all created things came, and by which they exist. The power of redemption is the power of creation, and that is the power of the life of Christ. The Sabbath is a great memorial of the wonderful works of God, which are the measure of His graciousness. He gave it that we might know that He is the Lord that sanctifies us.
Ellet J. Waggoner
The Cross is the demonstration of the power of God and of the inability of man.
The Cross is not just a singular event that happened about 2000 years ago. Revelation 13.8 "the Lamb was slain from the foundation of the world."
At creation God breathed out the breath of life into man; at the cross, Jesus breathed out His endless life that we might breathe it in.