So when they had gone through all the land, they came to Jerusalem at the end of nine months and twenty days.
So when they had gone through all the land,.... Beginning at the east, and from thence to the north, and then going about to the west, came to the south, which finished their circuit: they came to Jerusalem, at the end of nine months and twenty days: they were ten months wanting ten days in numbering the people; in which they seem to have been very expeditious.
Nine months and twenty days - This was a considerable time; but they had much work to do, nor did they complete the work, as appears from Ch1 21:6; Ch1 27:24. William the Conqueror made a survey of all England, particularizing "how many hides or carucates the land is taxed at; whose it was in the time of his predecessor Edward; who the present owners...
2Sa 24:8-9 When they had traversed the whole land, they came back to Jerusalem, at the end of nine months and twenty days, and handed over to the king the number of the people mustered: viz., 800,000 men of Israel fit for military service, drawing the sword, and 500,000 men of Judah. According to the Chronicles (1Ch 21:5), there were 1,100,000 Israelites and 470,000 Judaeans.
Commenting on 2 Samuel 24:8-9