"Keep thy heart with all diligence; for out of it are the issues of life." (Proverbs 4:23)
The Hebrew word nasar, here translated "keep," carries the strong idea of protection or guarding. It is used 10 times in Psalm 119 to stress the necessity of "keeping" (guarding, protecting) the various kinds of instructions in God’s Word: "testimonies, statutes, laws, precepts, and commandments." Everything written down by God is worth guarding.
In our text, the importance of guarding our hearts is emphasized since it is the source for the "issues of life." Jesus said, "A good man out of the good treasure of his heart bringeth forth that which is good; and an evil man out of the evil treasure of his heart bringeth forth that which is evil: for of the abundance of the heart his mouth speaketh" (Luke 6:45). Our "heart" is indeed the key to much in our life.
It is no wonder that the first commandment of all is to "love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength" (Mark 12:30).
Here are a few important principles that we must guard if our hearts are to produce the good "issues of life."
If our hearts do not condemn us, then we will have confidence with God (1 John 3:21).
"He that walketh uprightly, and worketh righteousness, and speaketh the truth in his heart" (Psalm 15:2) will live forever with the Lord of heaven and earth. HMM III