Jamieson, Fausset and Brown on Numbers 12:14

14. her father had but spit in her face, should she not be ashamed seven days?--The Jews, in common with all people in the East, seem to have had an intense abhorrence of spitting, and for a parent to express his displeasure by doing so on the person of one of his children, or even on the ground in his presence, separated that child as unclean from society for seven days.