Psalms 95:8-10. Harden not your heart as in provocation, and as in the day of temptation in the wilderness: When your fathers tempted me, proved me, and saw my work. Forty years long was I grieved with this generation, and said, it is a people that do err in their heart, and they have not known my ways.

 The heart in biblical language is the center of the human spirit from which springemotions, thoughts, motivation, courage & action, “the wellspring of life.” In Proverbs 4:2 it says “above all else guard your heart for it is the wellspring of life.”