The Sound Hearted Christian by William Greenhill and published by Soli Deo Gloria.
Nearing the end of his life and ministry, William Greenhill left his congregation a parting gift and lasting testimony of his pastoral care for their souls - he published The Sound-Hearted Christian. This book developed from a series of sermons Greenhill preached on Psalm 119:18, "Let my heart be sound in thy statutes; that I be not ashamed." Greenhill shows that a sound heart is watchful and attentive, recognizing that our soul is our greatest possession.
After demonstrating the excellence and desirability of a sound heart, he challenges us to test the soundness of our heart. He then directs and motivates us to get and keep a sound heart. The book ends with several appended sermons on faith, Christ, and God's Word, which serve as further encouragements to establishing and maintaining a sound heart.