Serious students of Isaiah - Jewish and Christian: What does this mean -?

A covenant is an agreement between two people. God promises to fight Israel's battles, if Israel will keep the commandments of God, including the keeping of the sabbath. To keep the sabbath, a person must not do any work or cause anyone else to work on the sabbath. The only work that is allowed is God's work. It is to be a day of spiritual renewal, a holy day, a day of rest.