Midrash sur Les Nombres 30:1

1) (Vayikra 17:2) ("Speak to Aaron and to his sons and to all the children of Israel and say to them: This is the thing that the L–rd has commanded, saying:") This teaches us that the children of Israel are commanded not to slaughter and bring an offering outside (the Temple court), but not gentiles. And, what is more, a gentile is permitted to build a bamah (a temporary altar) in all places and to offer sacrifices to Heaven. If (it were written only) "the children of Israel," I would know (that this applies) only to the children of Israel. Whence do I derive (that it applies also) to proselytes and bondsmen? From "and say to them." I might thing that (only) Israelites, who are commanded against offering sacrifices within (viz. Bamidbar 18:4), are commanded against slaughtering outside; but Aaron and his sons, who are not commanded against offering sacrifices within, are not commanded against slaughtering outside. It is, therefore, written ("Speak to) Aaron and to his sons." Whence is it derived that the heads of tribes are included here? It is written here "This is the thing," and elsewhere (Bamidbar 30:1, in connection with vows,) "This is the thing." Just as there, the heads of tribes (are specified), here, too, the heads of tribes (are intended). And just as here, Aaron and his sons and the children of Israel (are specified), so, there, Aaron and his sons and the children of Israel (are intended — See Nedarim 78b).