Song of Solomon 4:12
A spring shut up, a fountain sealed.
In this metaphor, which has reference to the inner life of a believer, we have very plainly the idea of secrecy. It is a spring shut up: just as there were springs in the East, over which an edifice was built, so that none could reach them save those who knew the secret entrance; so is the heart of a believer when it is renewed by grace: there is a mysterious life within which no human skill can touch. It is a secret which no other man knoweth; nay, which the very man who is the possessor of it cannot tell to his neighbour.
The text includes not only secrecy, but separation. It is not the common spring, of which every passer-by may drink, it is one kept and preserved from all others; it is a fountain bearing a particular mark - a king's royal seal, so that all can perceive that it is not a common fountain, but a fountain owned by a proprietor, and placed specially by itself alone. So is it with the spiritual life. The chosen of God were separated in the eternal decree; they were separated by God in the day of redemption; and they are separated by the possession of a life which others have not; and it is impossible for them to feel at home with the world, or to delight in its pleasures.
There is also the idea of sacredness. The spring shut up is preserved for the use of some special person: and such is the Christian's heart. It is a spring kept for Jesus. Every Christian should feel that he has God's seal upon him - and he should be able to say with Paul, "From henceforth let no man trouble me, for I bear in my body the marks of the Lord Jesus."
Another idea is prominent - it is that of security. Oh! how sure and safe is the inner life of the believer! If all the powers of earth and hell could combine against it, that immortal principle must still exist, for He who gave it pledged His life for its preservation. And who "is He that shall harm you," when God is your protector?