“Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints;” Ephesians 6:18

You know the book of 2 Samuel puts it casually what David did in 2 Samuel 24:1 , until you read this same account in 1 Chronicles and his decision making is demystified:
“And Satan stood up against Israel, and provoked David to number Israel.” 1 Chronicles 21:1
It was satan who moved David to walk in unrighteousness, and David insisted against Joab’s protestations as though the decision was being made consciously by him.
Yet another reason why you should pray for the saints.
Remember, as long as that person is a Christian, you share the same body irrespective of whether you like them and their position. Your preference of them was not consulted or irrelevant to the Holy Ghost when he baptized them into the body (1 Corinthians 12:13) and what that means is, it is for your own good if things go well with them (1 Corinthians 12:25, Hebrews 13:3), and so he admonishes that you pray for all saints! Pray like Epaphras- Colossians 4:12.
That they stand COMPLETE in God’s will, if David had been complete in God’s will, he’d have averted the plague that arose because of his decision because all he had to do was to tax the whole country during the census as God had instructed as a ransom for their lives, read more: Exodus 30:11-16.

Bible Reading Plan: Psalms 101, 2 Samuel 8