Reference for Nazir 6:1
שְׁלשָׁה מִינִין אֲסוּרִין בַּנָּזִיר, הַטֻּמְאָה וְהַתִּגְלַחַת וְהַיּוֹצֵא מִן הַגָּפֶן. וְכָל הַיּוֹצֵא מִן הַגֶּפֶן מִצְטָרְפִין זֶה עִם זֶה. וְאֵינוֹ חַיָּב עַד שֶׁיֹּאכַל מִן הָעֲנָבִים כַּזָּיִת. מִשְׁנָה רִאשׁוֹנָה, עַד שֶׁיִּשְׁתֶּה רְבִיעִית יַיִן. רַבִּי עֲקִיבָא אוֹמֵר, אֲפִלּוּ שָׁרָה פִתּוֹ בְיַיִן וְיֶשׁ בָּהּ כְּדֵי לְצָרֵף כַּזַּיִת, חַיָּב:
Three things are forbidden to a Nazirite: Uncleanliness [(Numbers 6:6): "Upon the soul of a dead one he shall not come."], shaving [(Ibid. 5): "A blade shall not pass over his head."], and what comes from the vine [(Ibid. 3): "And grapes, wet or dry, he shall not eat."] And everything that comes from the vine [such as grapes, wet and dry, kernels and husk] combine with each other [to an olive-size, making one liable to stripes.] And he is not liable until he eats an olive-size of grapes. And the quantity for drinking is, likewise, an olive-size. For since it is written: "And grapes, wet and dry, he shall not eat," we derive: Just as with eating, an olive-size, so with drinking, an olive-size.] An earlier Mishnah: (He is not liable) until he drinks a revi'ith of wine. [The earlier Mishnah apprises us that we derive it in the opposite manner, eating from drinking. And the quantity for drinking for a Nazirite (to be liable) is a revi'ith, this being derived "shechar" (strong drink) (Numbers 6:3) - "shechar" (Leviticus 10:9), from (what is written in respect to) the sanctuary. And just as the prohibited drinking quantity is a revi'ith, so the prohibited eating quantity is a revi'ith.] R. Akiva says: Even if one soaks his bread in wine and there is enough to combine to an olive-size, he is liable. [R. Akiva holds that the prohibited quantity for a Nazirite, both for eating and for drinking is an olive-size, and the permitted (food) combines with the forbidden to complete the (forbidden) quantity. The halachah is not in accordance with R. Akiva.]