Nazir 40B

אין קרבנו בדלות. תאמר במצורע שקרבנו בדלות!

the offering in each case does not include a level of poverty. In both cases the offering is fixed, i.e., a poor person does not have the option of bringing a less expensive offering due to his financial straits. Will you say the same with regard to the metzora, whose offering includes a level of poverty, as a poor person can bring turtledoves instead of sheep (Leviticus 14:21–22)? Since the Torah was more lenient in the case of a metzora than the cases of a nazirite and the Levites, it could also be that the halakha is also lenient with regard to his shaving, by not demanding the use of a razor. Consequently, there is no proof that a metzora is obligated to shave with a razor.

אמר ליה רבא בר משרשיא לרבא: האי תנא, מעיקרא אמר: ללמדו ממצורע אי אפשר, שאין דנין קל מחמור להחמיר עליו. והדר אמר: נילף מדינא, ומדינא נמי לא יליף?

In continuation of this discussion, Rava bar Mesharshiyya said to Rava: This tanna initially said, with regard to the obligation of a nazirite to shave with a razor (39b): It is impossible to learn this requirement from the halakha that a metzora must use a razor, as one does not derive a halakha in a lenient case from the halakha in a more stringent one in a manner that would cause one to be stringent in the more lenient case. This indicates that it is obvious to the tanna that a metzora himself must shave with a razor. And he then said: Let us derive by means of an inference that a metzora must use a razor, and ultimately he did not derive it from an inference by analogy either, due to Rava of Barnish’s objection. What, then, is the source for the halakha that a metzora must use a razor?