Charles Ellicott Commentary 1 Chronicles 21:4

"Nevertheless the king`s word prevailed against Joab. Wherefore Joab departed, and went throughout all Israel, and came to Jerusalem." — 1 Chronicles 21:4 (ASV)

So Joab departed. —“Went out,” namely, from the king’s presence (Samuel). The chronicler omits the account of the route of Joab and his party, as described in 2 Samuel 24:4–8. They crossed Jordan, and went to Aroer, Jazer, Gilead, and Dan; then round to Zidon, “the fortress of Tyre, and all the cities of the Hivite and Canaanite, and came out at the nageb of Judah, to Beersheba.” The business occupied nine months and twenty days; and the fact that the generalissimo of David’s forces and his chief officers found leisure for the undertaking indicates a time of settled peace. The census, therefore, belongs to the later years of the reign.