Parashas Naso · Passuk 6:14
As an offering to GOD they shall present: one male lamb in its first year, without blemish, for a burnt offering; one ewe lamb in its first year, without blemish, for a purgation offering; one ram without blemish for an offering of well-being;
Chabad.org — English translation + Rashi
Source: Nazir 45b.
English: “For a sin-offering and one ram” — Scripture compares the ram to the sin-offering: if he shaved after any one of the three offerings, he has fulfilled [the requirement].
In context: Although ideally all three offerings precede the haircutting, the midrash validates shaving after any single one of them.
Custom
Chazal teach that shaving after any one of the three concluding offerings discharges the nazir’s hair obligation.