From an excellent piece by Dallas Willard called "The Key to the Keys to the Kingdom":

What are some practices that will make "the keys" given in response to our faith in Jesus as Messiah effective in our lives as ministers? We strongly need to see the manifest hand of God in what we are and what we do. We need to be sure He is pulling the load, bearing the burden--which we are all too ready to assume is up to us alone. We must understand that He is in charge of the outcome of our efforts, and that the outcome will be good, right. And all of this is encompassed in one biblical term, "Sabbath."

The Sabbath, Jesus said, was made for man. (Mark 2:27) That is, it serves human life in essential ways. Without it, life cannot be what it should be. That is why it is given in the Ten Commandments, at the heart of the moral law. It is not something we have to do because God has arbitrarily required it of us, a pointless hoop He would have us jump through. It is His gift to us. At the same time it makes clear that our life and our ministry is also His gift to us.Sabbath is a way of life. (Heb. 4:3 & 9-11) It sets us free from bondage to our own efforts. Only in this way can we come to the power and joy of a radiant life in ministry, a blessing to all we touch. And yet Sabbath is almost totally absent from the existence of contemporary Christians and their ministers.

What is Sabbath? Biblically, it is a day, once a week, when we do no work. "Six days you shall labor and do all your work, but the seventh day is a sabbath of the Lord your God; in it you shall not do any work." (Ex 20:9-10) It was also a year, once every seven years, when God's covenant people not sow seed, prune vines or store up harvest. (Lev. 25:4-7) And to the question, "How are we going to eat in the seventh year?" God replied: "I will so order My blessing for you in the sixth year that it will bring forth the crop for three years." (vs. 21)

The moral principle certainly applies as well to our non-agrarian, contemporary life, though our faith will be greatly challenged in working out the details. Very practically, Sabbath is simply "casting your cares upon Him," to find that in actual fact "He cares for you." (I Peter 5:7) It is using of the keys to the kingdom to receive the resources for abundant living and ministering.