In this sermon on Proverbs 4:23, Charles Spurgeon uses the metaphor of a water reservoir to teach that just as a city's water supply depends entirely on the central reservoir's condition, so all of life flows from the heart, making it futile to try reforming behavior, educating the mind, or strengthening the will without first addressing the heart itself. He urges Christians to keep their hearts full (by drawing constantly from God through prayer, Scripture, and communion with Christ rather than living spiritually dry lives), pure (by fixing the cross of Christ in their hearts rather than allowing sin to pollute them), peaceful (by maintaining calmness through the Holy Spirit's work rather than letting inner turmoil create outer conflicts), and undivided (by serving Christ wholeheartedly rather than trying to walk both sides of the street by giving some affection to God and some to the world). Spurgeon concludes that a heart enriched with God's Word, generous love, and Christ's presence will produce a life that blesses others like wine instead of water, while warning unconverted people that their stony hearts need complete replacement by God's regenerating power.

Sermon delivered on February 21, 1858.