Adam Clarke on Exodus 2:17

The shepherds - drove them - The verb יגרשים yegareshum, being in the masculine gender, seems to imply that the shepherds drove away the flocks of Reuel's daughters, and not the daughters themselves. The fact seems to be, that, as the daughters of Reuel filled the troughs and brought their flocks to drink, the shepherds drove those away, and, profiting by the young women's labor, watered their own cattle. Moses resisted this insolence, and assisted them to water their flocks, in consequence of which they were enabled to return much sooner than they were wont to do, Exo 2:18.