The man is as his heart is. The heart is the spring and fount of all natural and spiritual actions, it is the _primum mobile,_ the great wheel that sets all other wheels agoing; it is the great monarch in the isle of man, therefore, keep it with all custody and caution, or else bid farewell to all true joy, peace, and comfort. When the heart stands right with Christ He will pardon much and pass by much. . . . Therefore we should keep our heart as under lock and key, that they may be always at hand when the Lord shall call for them. . . . The word heart is here put comprehensively for the whole soul, with all its powers, noble faculties, and endowments, together with their several operations, all which are to be watched over. . . . It is a duty incumbent upon every Christian to keep his own heart. Thou mayest make another thy park-keeper, thy housekeeper, thy shopkeeper, thy cash-keeper, but thou must be thy own heartkeeper. "With all diligence." Some understand this of all kind of watchfulness. 1. As men keep a prison. How vigilant are they in looking after their prisoners. 2. As they keep a besieged garrison, or castle, in time of war. A gracious heart is Christ's fort-royal. Against this fort Satan will employ his utmost art, therefore it must have a strong guard. 3. As the Levites kept the sanctuary of God and all the holy things committed to their charge (Ezek. xliv. 8-15). Our hearts are the temples of the Holy Ghost, and therefore we should keep a guard about them, that nothing may pass in or out that may be displeasing, grieving, or provoking to Him. 4. As a man keeps his life. The same word (_shamar_) is used in Job. x. in reference to life. With what care, what diligence, do men labour to preserve their natural lives. 5. As men keep their treasures. There are few men who know how to value their hearts as they should. It is that pearl of price for which a man should lay down his all. 6. As spruce men and women do their fine clothes. They won't endure a spot upon them. Let not others be more careful to keep their outsides clean, than you are to keep your insides clean.--_Brooks._ The fountains and wells of the East were watched over with special care. A stone was rolled to the mouth of the well, so that "a spring shut up, a fountain sealed," became the type of all that is most jealously guarded (Song Sol. iv. 22). So it is here. The heart is such a fountain--out of it flow "the issues of life." Shall we let the stream be tainted at the fountain head?--_Plumptre._