Guard your heart above all else, for it is the source of life.
Proverbs 4:23 CSB
Solomon’s dad felt he could nail down a sinless life (from some point onward!) by storing up (tsafan, צפן) God’s word in his heart. The whole assembly of Hebrews at Sinai, pledging to do what YHWH says, were not blessed with a heart that could contain God’s message.
Heart and soul, exceedingly
All the way to New Testament times few men, knew what it was to have God’s word on the inside. Prophets and wise men, not knowing what they were hearing, clung to reciting the words of God and adorning their bodies and clothing with bits of “Bible” quite literally.
One God is where security starts and we have seen that the people who say they are champions of all the right things have the hardest time getting past the first step. Only the bewitched believe that life comes from what goes into the heart or body.
Life comes from God, Solomon, but that is ok, you did not know, and Moses was not a big deal did you.
Source of life: heart and mouth
Did we not learn that the heart is the source of human badness?
For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, slander, pride, foolishness. Mark 7:21-22
For Moses wrote about life when he discussed the righteousness that is based on the law, namely, that the person who does the commandments shall live by them. Solomon was a dismal failure in this regard.
But the righteousness based on faith says, Do not say in your heart, Who will ascend into heaven? (that is, to bring Christ down) or Who will descend into the abyss? (that is, to bring Christ up from the dead).
Moses would not be surprised that now a new arrangement rules the life-flow. He predicted the shift to an effective word of faith.
But what does it say? The word is near you, in your mouth and in your heart (that is, the word of faith that we proclaim); because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. Romans 10:5ff