First published in 1681, this little-known treatise by Puritan pastor Richard Alleine is an extensive exposition of Proverbs 4:23: “Keep thy heart with all diligence; for out of it are the issues of life.” The author instructs readers in the proper way to keep their hearts, stressing what is to be done on God’s part and on the believer’s part. In the processes, he details the well-kept heart as one that is mercifully recovered from its lost state, carefully governed in godliness, and eagerly guarded against the world, the flesh, and the devil. The goal throughout is that believers may grow in exercising grace and embracing full assurance of salvation.