Midrash sur Les Nombres 6:10

(Bamidbar 6:10) "And on the eighth day he shall bring, etc.": to exclude the seventh day. You say, to exclude the seventh day; but perhaps, to exclude the ninth day? Would you say that? If (the eighth day), which is close to the forbidden (seventh day), is permitted, how much more so should (the ninth day), which is close to the permitted (eighth day) be permitted! — This is refuted by the time for eating the Paschal offering, where the time (the night of the fifteenth of Nissan), which is close to the forbidden (the day preceding that night) is permitted, and (after midnight on the night of the fifteenth), which is close to the permitted, is forbidden. Do not wonder, then, about this (forbidding of the offering on the ninth day) that even though what is close to the forbidden is permitted, what is close to the permitted is forbidden. We have not succeeded (with this argument). Let us derive it from the offered (i.e., the animals offered on the altar.) A time has been fixed for the offered (viz. Vayikra 22:17) "From the eighth day (of its birth) on it shall be accepted as a fire-offering"), and a time has been fixed for the offerers ("And on the eighth day he shall bring, etc." Just as with the offered, the eighth day and beyond was permitted, so, with the offerers. And, furthermore, it follows a fortiori, viz.: If with the offered, where Scripture enumerates many that are unfit (for offerings), it validates (offerings) of the eighth day and beyond, how much more so with the offerers, where Scripture did not enumerate many that are unfit, should (offering) be validated from the eighth day and beyond! — No, this may be so with the offered, this time obtaining with all offerings, wherefore the eighth day and beyond was permitted, would you say the same for the offerers, where this time does not obtain for all, (but only for the Nazirites) — wherefore it would not be permitted from the eighth day on. I have not succeeded with ratiocination; I derive it by identity (gezeirah shavah ), viz.: It is written here (in the instance of the Nazirite) "the eighth day," and elsewhere (in the instance of the offerings), "the eighth day." Just as there, the eighth and beyond is validated, so, here.

"two turtle-doves or two young pigeons" — whence they ruled: Turtle-doves cannot be substituted for pigeons nor pigeons for turtle-doves. "to the Cohein, to the door of the tent of meeting": We are hereby taught that it is his obligation to care for them until he brings them to the door of the tent of meeting.