We have been discussing a case where someone accepts nezirut upon himself while standing in a cemetery, creating a situation where the nezirut begins in a problematic situation of tumah. Which is a greater defilement: a situation where a nazir comes into contact with a dead body, or one in which the actual nezirut begins in a state of tumah?
The Gemara explains that we may have thought that the latter was the greater defilement and that just as a nazir who becomes tameh must have his hair cut off and bring sacrifices (see Bamidbar 6:9-10), so too would someone who established his nezirut under forbidden circumstances be obligated. However, examination of the passage ve-timeh rosh nizro – “…and he defiles his consecrated head,” (Bamidbar 6:9) leads the Gemara to conclude that this is not the case. In fact, only the nazir who actively becomes tameh needs to cut his hair and bring sacrifices; the individual who was never a nazir tahor (a ritually pure nazir) is not subject to these requirements.
Tosafot explain that the Gemara derives this from the words ve-timeh rosh nizro because those words are superfluous – the entire law could have been taught without them. Thus the Gemara concludes that they are written in order to emphasize that it is only someone who had been a nazir and became tameh who has to have his hair cut and is obligated to bring the sacrifices of a nazir tameh.
When referring to the sacrifices of the nazir, the Gemara specifically mentions tzipporim – the doves that are brought by the nazir who becomes tameh. Tosafot and other rishonim point out that the Gemara is bringing the tzipporim as an example, but the rule would be the same for all of the sacrifices of a nazir tameh.