Rashi on Genesis 17:11/רש"י על בראשית י״ז:י״א

1ונמלתם AND YE SHALL CIRCUMCISE — This word, in spite of the נ in it, is not Niphal but the same as ומלתם and the נ in it is an addition to the root, which only sometimes appears in it, as, for example, the נ of נושך and of ונמלתם ;(נושא is Kal like ונשאתם “and ye shall carry” (Genesis 45:19), but יִמּוֹל (Genesis 17:12 and Genesis 17:13) is a Niphal form — “shall be circumcised” — like יֵעָשֶׂה “it shall be done”, and יֵאָכֵל “it shall be eaten”.