I Chronicles 21:1 and 2: Satan Tempts us to put our trust in that which we possess. It is his desire that we trust in our own efforts and in all we can accumulate. We are to trust in God alone (Luke 12:13-21).
I Chronicles 21:3: Joab gives David Godly council. Nothing is of more value than solid Godly council (Proverbs 11:14). Joab reminds David that the people are not his; they are the Lord’s people (Exodus 4:22).
I Chronicles 21:4-7: David rejects Godly council. God spoke to him through Joab. Rejection of God’s word always results in sin and it’s consequences (Psalm 119:11). When we willfully sin by doing what we know is wrong, it is a horrible sin (Romans 14:23).
I Chronicles 21:8: We hope for God to spare us the consequences of our own sinful actions, but God will not be mocked (Galatians 6:7).
I Chronicles 21:9-12: God is displeased with David and tells him to choose his punishment. All of the choices ultimately affect only the people of Israel. Often those we hold dear, suffer the consequences of our sin (Proverbs 15:27 and 17:13).
I Chronicles 21:13 and 14: David chooses a plague and 70,000 die as a result of his sin. Sin always has consequences (II Samuel 11:4 and 5).
I Chronicles 21:15-17: David repents of his sin and God is merciful. If we turn from sin, God always shows us mercy as well (II Chronicles 6:14 and 26 and 27).