Torah and Mitzvahs for Personal Motives
Rav Yehuda said in the name of Rav, “One should always be involved in learning Torah and fulfilling mitzvot even if not for the purest reasons, because this will lead to learning and fulfilling for pure reasons.”
An important caveat: This encouragement applies to motives of personal gain; but one who learns Torah as a means to gain knowledge to try to refute or degrade it is “better off unborn”. (Tosefot)
“In the reward of the forty-two sacrifices that the wicked Balak offered, he merited that Ruth would be descended from him.”
This is an example of the ruling of Rav Yehuda in the name of Rav that it is a positive measure to fulfill a mitzvah even if it is only for personal motive. The gemara explains Ruth’s lineage from the king of Moav as follows: Rabbi Yossi the son of Rabbi Chanina said, “Ruth was the daughter of the son of Eglon, the king of Moav”.
Argument about a Mistake
“Beit Shammi says, ‘Hekdesh made in error is indeed hekdesh’; and Beit Hillel says ‘It is not hekdesh’.”
This mackloket is taught in our mishna, and Tosefot explains why it is taught in this masechet about Nazir and not about hekdesh. One reason offered is that a later mishna teaches about “nezirut made in error.”
One example of “hekdesh made in error” is if a person vows that the black ox that goes out from his house in the morning first will be hekdesh — and a white ox goes out first. The white ox is hekdesh according to Beit Shammai but not according to Beit Hillel. A different way to explain their dispute is that Beit Shammai holds that the first black ox that goes out after the white one is hekdesh, but not the white one that actually went out first.
Nazir 30b, 31a