Gold and silver, those precious metals, take no injury, receive no spot of corruption from the vessel in which they are contained; let them be buried in the damp earth, no tarnish or rust forms upon them. So spiritually, the grace of God in the heart, surrounded as it is with corruption, is not tarnished by it, the heavenly treasure is not contaminated, though lodged in an earthen vessel.
Christ in the heart is not defiled by the inward workings of depravity, and by the base thoughts that strive perpetually against his grace, any more than the gold of the Bank of England is defiled by the dark and damp cellars in which it is stowed. And what a mercy it is, that our corruptions cannot tarnish the grace of God; that our unbelief cannot mix with, and adulterate the faith of God's elect; that our despondency cannot spoil and ruin a gospel hope; that our deadness, darkness, coldness, and rebellion cannot mingle with and defile the love of God in the soul!
This heavenly treasure remains still as unpolluted and pure as when God first put it there; being a part of "the divine nature," it remains uncontaminated by the filth and corruption that surround it. Is not this a mercy for God's tried people, that spiritual knowledge, living faith, gospel hope, heavenly love, and the fruits and graces of God's Spirit in the soul can never be defiled; but, like the streams of a fountain, are ever gushing forth in pure water?
What a blessing it is, that the pure grace of God in a man's heart cannot be contaminated by the filthy streams that are dashing from a vile nature against it, like the torrents of water from a fire-engine against a burning house, but remains as pure as when God the Spirit first breathed it into the soul.