And He said to them, “The Sabbath was made for man, and not man for the Sabbath. Therefore the Son of Man is also Lord of the Sabbath.” (Mark 2:27–2)
The third precept is: Remember to keep holy the Sabbath day. In this third commandment is suggested a certain idea of freedom, a repose of the heart or tranquillity of the mind which a good conscience effects. Indeed, sanctification is there because the Spirit of God dwells there. Now look at the freedom or repose; our Lord says: Upon whom shall I rest but upon the man who is humble and peaceable, and who trembles at my words? Therefore, restless souls turn away from the Holy Ghost. Lovers of strife, authors of calumnies, devotees of quarrels rather than of charity, by their uneasiness they do not admit to themselves the repose of a spiritual sabbath. Men do not observe a spiritual sabbath unless they devote themselves to earthly occupations so moderately that they still engage in reading and prayer, at least frequently, if not always. As that Apostle says: Be diligent in reading and in teaching; and again: Pray without ceasing. Men of this kind honor the sabbath in a spiritual manner. However, restless souls are continually involved in earthly activity, and of them it is written: “The burdens of the world have made them miserable.” They are unable to have a sabbath, that is, repose. In reply to their restlessness, it is said that they should have, as it were, a sabbath in their heart and the sanctification of the Spirit of God: Be swift to hear, it says, but slow to answer. Cease your uneasiness, let there not be a tumult in your heart because of phantoms flying about to corrupt you, disturbing and pricking you like flies. You are to realize that God is saying to you: Desist! and confess I am God. By your restlessness you do not want to be still; blinded by the corruption of your contentions you demand to see what you cannot. Notice the opposite third plague which is contrary to this commandment. Sciniphs sprang up out of the mud in the land of Egypt, very tiny flies, exceedingly restless, flying around in confusion, rushing into one’s eyes, not allowing a man to rest, coming back while they are being driven away, returning again even when expelled. Restless men are like these little flies, when they refuse to observe the sabbath in a spiritual manner, that is, to be zealous for good works and to engage in reading or prayer. Doubtless, such are the phantoms of quarrelsome hearts; just as the human body is tormented by those flies, so their hearts are disturbed and pricked by opposing thoughts. Keep the commandment, but guard against the plague.
Caesarius of Arles, Sermon 100.4