Jamieson, Fausset and Brown on 2 Samuel 24:6

6. the land of Tahtim-hodshi--that is, the land lately acquired; namely, that of the Hagarites conquered by Saul (1Ch 5:10). The progress was northward. Thence they crossed the country, and, proceeding along the western coast to the southern extremities of the country, they at length arrived in Jerusalem, having completed the enumeration of the whole kingdom in the space of nine months and twenty days.