"You shall love the Lord your God with all your heart and with all your soul and with all your mind." (Matt 22:37)
He highlighted the word 'all' showing that Jesus calls for "surrender that is extreme" & that "you cannot hold anything back." He explained that the Hebrew word 'lebab shalem' (Used throughout the Old Test. concerning a whole heart) means to be 'Wholeheartedly devoted'.
David compared 2 guys from the Old Testament showing opposing sides of this.
First: Solomon who knew God's desire for whole hearted love yet as the years passed he disobeyed, compromised & allowed himself to be distracted in many areas that were against God's law.
In his old age his heart had drifted far from God.
Second: Caleb, who we see first as one of the spies sent into Canaan by Moses, and then in old age (85) in Joshua 7:1-14. This guy had not wavered one bit in his devotion to God and was much the same (if not more devout & trusting) at 85 as he had been at age 40.
In his old age his heart had remained devoted to God.
David's question was simply:
"Who's heart have you; Caleb's or Solomon's?"
As in all areas, by exercising that area it becomes stronger. And so David gave pointers as to what Scripture calls us to do with our whole hearts, so that if we practise these we may grow to have 'Caleb hearts' rather than 'Solomon hearts'.
Whole heartedly...
As David reminded us when talking about the wise Solomon:
"It is never enough to know Scripture without implementing & obeying it."