Commentary for Numbers 1:2

למשפחתם — [TAKE YE THE SUM OF THE CONGREGATION …] AFTER THEIR FAMILIES — in order to ascertain the number of individuals in each tribe.

שאו את ראש, to organise them so that they could proceed to the land of Israel immediately, without delay, each one of them knowing to which unit (flag) he belonged. At that point, no war of conquest had even been envisaged, the assumption having been that G’d would remove the inhabitants of the land of Canaan so that no face-to-face encounter would even be necessary. Evidence from Isaiah 17,9 suggests that in fact, at least partially, this even occurred after the 40 years in the desert. The prophet there reports that once again, as at the time when the Emorite and the Hittite abandoned their cities in the face of the advancing armies of the Israelites, history will repeat itself. [based on the Septuagint. Our author assumes that Isaiah may have referred to the tribe of the Girgashi, quoting Jerusalem Talmud Sh’viit 6,1 Ed.]
At any rate, due to the sin of the spies the seven Canaanites nations survived another 40 years during which they added to their sins so that at the end of that time G’d did not merely exile them but exterminated them.

שאו את ראש כל עדת בני ישראל, "Count the whole community of Israel, etc." We need to know why the Israelites had to be numbered at this time. Rashi quotes a Midrash according to which G'd ordered the census as soon as He was ready to again allow His Presence to dwell amongst the Israelites (after the sin of the golden calf). This is insufficient to answer our question. If the census had only been an indication of G'd's reconciliation with His people He should have ordered it to take place before the month of Nissan when the Tabernacle was inaugurated, not a month later.