For the men of war had taken spoil, every man for himself. And which he kept for himself, and did not deliver in with the prey or booty, which was brought to Moses and Eleazar, the sum of which was taken by them; and this seems to confirm what has been hinted, that, as each soldier had taken spoil for himself, so everyone contributed his quota towards this freewill offering to the Lord.
Numbers 31:54

officers . . . said . . . there lacketh not one man of us--A victory so signal, and the glory of which was untarnished by the loss of a single Israelitish soldier, was an astonishing miracle. So clearly betokening the direct interposition of Heaven, it might well awaken the liveliest feelings of grateful acknowledgment to God (Psa 44:2-3). The oblation they brought for the Lord "was partly an atonement" or reparation for their error (Num 31:14-16), for it could not possess any expiatory virtue, and partly a tribute of gratitude for the stupendous service rendered them. It consisted of the "spoil," which, being the acquisition of individual valor, was not divided like the "prey," or livestock, each soldier retaining it in lieu of pay; it was offered by the "captains" alone, whose pious feelings were evinced by the dedication of the spoil which fell to their share. There were jewels to the amount of 16,750 shekels, equal to £87,869 16s. 5d. sterling.

Next: Numbers Chapter 32