Números 12:14 Comentario: Rashi, Sforno, Or HaChaim & Rabbeinu Bahya

ואביה ירק ירק בפניה IF HER FATHER HAD BUT SPIT IN HER FACE — i.e. if he had shown her an angry face (if he was offended with her), הלא תכלם שבעת ימים SHOULD SHE NOT BE PUT TO SHAME FOR SEVEN DAYS? — It follows therefore à fortiori with respect to the Shechinah (i.e. in the case where God rebukes her in such a stern way) that she ought to be put to shame for fourteen days!) But since there is a rule דין לבא מן הדין להיות כנדון “It is sufficient for a law that is derived by a conclusion a fortiori (הבא מן הדין) to be only as strict as the law from which it is derived (נדון), and not go beyond it, therefore even as a consequence of My reprimand, תסגר שבעת ימים LET HER BE SHUT OUT [FROM THE CAMP] SEVEN DAYS only (Sifrei Bamidbar 106; Bava Kamma 25a).

הלא תכלם, she deserves to experience this shameful embarrassment.

ואביה ירוק ירק, "if HER father had spit in her face, etc." The Torah emphasises Miriam's experience as that of a daughter of G'd, i.e. a צדקת, rather than that of any father spitting at any daughter.