Spit in her face, i.e. expressed some eminent token of indignation and contempt, which this was, Job 30:10 Isaiah 1:6. Should she not be ashamed, and withdraw herself from her father's presence? as Jonathan did upon a like occasion, 1 Samuel 20:34. So though God healed her according to Moses's request, yet he would have her publicly bear the shame of her sin, and be a warning to others to keep them firm the same transgression. Seven days, the time appointed for cleansing the unclean. See Numbers 6:9, Numbers 31:19.
Related Commentaries of Numbers 12:14
Numbers 12:14
14 And the LORD said unto Moses, If her father had but spit in her face, should she not be ashamed seven days? let her be shut out from the camp seven days, and after that let her be received in again.