Abel obeyed God and kept his commandment, and God accepted Abel because of his obedience.
Genesis 4:4

God created and commanded that we should keep his Seventh Day Sabbath as the day of rest. Just as God accepted Abel, so God will accept us if we keep and remember his Seventh Day Sabbath.
Genesis 2:1-3 the creation of the Seventh Day Sabbath.

The Commandment of God to keep and remember the Seventh Day Sabbath:
Exodus 20:8-11 The Fourth Commandment of the Ten Commandments.
Deuteronomy 5:12-15 The Fourth Commandment of the Ten Commandments.