Сифрей Мицвот к Бамидбар 19:21

וְהָיְתָ֥ה לָּהֶ֖ם לְחֻקַּ֣ת עוֹלָ֑ם וּמַזֵּ֤ה מֵֽי־הַנִּדָּה֙ יְכַבֵּ֣ס בְּגָדָ֔יו וְהַנֹּגֵ֙עַ֙ בְּמֵ֣י הַנִּדָּ֔ה יִטְמָ֖א עַד־הָעָֽרֶב׃

И это будет вечный устав для них; и тот, кто окропляет водой, окропит одежду свою; и тот, кто прикоснется к воде кропления, будет нечист до смирения.

Sefer Hamitzvot of Rasag

The one who sprinkles the water for impurity must launder

Sefer Hamitzvot of Rasag

And similarly one who touches them becomes impure. Gimel Concluded are the forty five commandments about separating impurity, not to approach it. Included were one hundred and three priestly commandments, which are intertwined with them. Bet Among them were included the first set, in total two hundred practices. Aleph These are the positive commandments that the lofty Sages discussed.