Adam Clarke on Job 1:17

The Chaldeans made out three bands - The Chaldeans inhabited each side of the Euphrates near to Babylon, which was their capital. They were also mixed with the wandering Arabs, and lived like them on rapine. They were the descendants of Chesed, son of Nahor and brother of Huz, from whom they had their name Casdim, which we translate Chaldeans. They divided themselves into three bands, in order the more speedily and effectually to encompass, collect, and drive off the three thousand camels: probably they mounted the camels and rode off.