When we read these two passages side by side, apparent discrepancies are highlighted. Let’s think through those briefly.
As to who incited David to take the census, there truly is no discrepancy if we recall how Satan accused Job before God, and received God’s permission to attack Job. Why would God let Satan incite Him against His people that way? In this case there apparently was a sin problem in Israel that God was ready to address, and the three options He gave David for punishment were ways He had warned them He would use if they did not follow Him. Satan’s accusations apparently worked into His plan for disciplining His people.
What was wrong with David’s taking a census of his people? Although it wasn’t evident to us, the sin in the matter was evident to Joab and apparently to other leaders over whom David’s superior position prevailed. Most importantly, it was evident to David. Bible scholars believe the objections and David’s confession point to an issue of pride in David’s heart, and his plan to rely on the strength of his military rather than on God for security. That the sin isn’t evident to us reinforces the reality that God is aware of the thoughts and intents of our hearts even when they are not evident to others.
The difference in the numbers counted in the census can be attributed to any number of factors. One is that accounting method they used back then (have I addressed that before?) that counted parts as wholes, making their accounting a lot less accurate than we make ours today. Their difference in rounding numbers, added to the possibility of the addition or omission of a single dot in copying the text in ancient times yielding different numbers in translation, added to the difference in reckoning who was Israel and who was Judah, explain the difference. Further, it seems to me that the numbers given are rather loose anyway, since Joab took it upon himself to fudge them by omitting two of the tribes. Which of these might be included in the numbers in I Chronicles?
From the incident on Araunah’s threshing floor, God finally indicated the place for a temple to be built to house the Ark of the Covenant. This would be the place in which the entire nation would gather to observe their required pilgrimage holy days, the place where God would place His name. Interestingly, it was the spot where Abraham had built an altar on which to sacrifice Isaac hundreds of years earlier. Now it was again a place where God showed mercy in accepting an alternate sacrifice. Why don’t you contemplate the significance of God’s choosing that site as the place in which He would be present among His people? What does that teach you about God?