Nedarim 9B

כי קאמר רבי מאיר ⁠— בנדר, בנדבה לא קאמר. והא קתני: ״כנדבותם״⁠ — נדר בנזיר ובקרבן! תני: נדב בנזיר ובקרבן.

When R' Meir said that one should abstain from making vows, he was referring only to a vow; he did not say it with regard to a gift offering. The Talmud asks: But it is taught in the Mishnah that if one said: Like the gift offerings of the virtuous, he has vowed with regard to becoming a nazirite or bringing an offering; this indicates that the virtuous vow to become nazirites and bring offerings. The Talmud answers: Teach the Mishnah in the following emended formulation: He has volunteered with regard to becoming a nazirite or bringing an offering.

מאי שנא נודר דלא ⁠— דלמא אתי בה לידי תקלה? נדבה נמי לא ⁠— דלמא אתי בה לידי תקלה!

The Talmud asks: What is different about one who vows, i.e., one who says: It is incumbent upon me to bring an offering, which is not proper to do due to the concern that perhaps he will encounter a stumbling block and not bring it promptly, thereby violating the prohibition against delaying? One should also not designate a particular animal as a gift offering due to the concern that perhaps he will encounter a stumbling block with it. Once the animal is consecrated, anyone who unwittingly benefits from it, e.g., by shearing it or working with it, transgresses the prohibition against misusing consecrated property.

כהלל הזקן. דתניא: אמרו על הילל הזקן שלא מעל אדם בעולתו כל ימיו. מביאה כשהיא חולין לעזרה, ומקדישה, וסומך עליה, ושוחטה.

The Talmud answers: In the case of a gift offering, he can act like Hillel the Elder. As it is taught in a baraita: They said about Hillel the Elder that no person misused his burnt-offering in his lifetime. How did he ensure this? He was careful not to consecrate the animal in advance; rather, he would bring it when it was unconsecrated to the Temple courtyard and there he would consecrate it, and then immediately he would place his hand on its head and slaughter it. Consequently, there was no opportunity to misuse it.