There are a few distinct moments where David is confronted about his pride. One of them comes shortly after a streak of victorious military battles. Israel has been reigning supreme and yet David opts to take a census - to count how many fighting men he has at his disposal. 

Yet God reads through this and sees David’s action as being one of trusting in man’s strength. It doesn’t matter that there are one million - one hundred thousand men who could handle a sword, this request insinuates a lack of trust in the one who was truly providing victory. 

What strikes me most about this exchange from 1 Chronicles 21 is actually what happens after David’s recognition of sin and God’s pardon of judgement. David builds an altar and the Jebusite Araunah offers his oxen to sacrifice. David responds in 1 Chronicles 21:24, “No, I insist on paying the full price. I will not take for the Lord what is yours, or sacrifice a burnt offering that costs me nothing.” 

This signals a significant character change in David’s life. His census had underlying greed, and now his sacrifice has underlying trust. If your faith doesn’t cost you something, it’s not worth trusting in.