Reference for Nazir 2:1
הֲרֵינִי נָזִיר מִן הַגְּרוֹגָרוֹת וּמִן הַדְּבֵלָה, בֵּית שַׁמַּאי אוֹמְרִים, נָזִיר, וּבֵית הִלֵּל אוֹמְרִים, אֵינוֹ נָזִיר. אָמַר רַבִּי יְהוּדָה, אַף כְּשֶׁאָמְרוּ בֵית שַׁמַּאי, לֹא אָמְרוּ אֶלָּא בְאוֹמֵר הֲרֵי הֵן עָלַי קָרְבָּן:
(If one said:) "I shall be a Nazirite from dried figs or pressed figs" (to which Naziritism does not apply), Beth Shammai say: He becomes a Nazirite, and Beth Hillel say: He does not become a Nazirite. [Beth Shammai hold that one does not utter things in vain, and that when he said: "I shall be a Nazirite," he meant it — so that when he continued: "from dried figs or pressed figs," he meant to retract. And even in the midst of his words he cannot retract, Beth Shammai holding that hekdesh ("dedication") in error remains hekdesh, and is susceptible neither of absolution nor retraction. And the same applies to Naziritism, it being written in that regard (Numbers 6:5): "Holy shall he be" — for which reason he becomes a Nazirite. And Beth Hillel hold that since he did not vow in the manner of vowers, he does not become a Nazirite, there being no such thing as Naziritism from dried figs or pressed figs.] R. Yehudah said: Even when Beth Shammai said what they did, they said so only when he thought (in his heart): "They are (forbidden) to me as an offering (is forbidden)." [Beth Shammai do not differ with Beth Hillel as to his not becoming a Nazirite. They differ only when he says: I intended that the figs be (forbidden) as an offering (is forbidden) to me. Beth Shammai hold him to be bevowed from figs; Beth Hillel do not.]