משנה על שמות 12:15

If one has eaten of [these five] on Pesah an olive-size piece of matzah, he has fulfilled his obligation. [If he ate on Pesah] an olive-size of piece of hametz [made of these grains], he is liable for karet. If one of these [grains, having become leavened,] became mixed with any other species, one must remove it on Pesah. If one has vowed [to abstain] from [consuming] bread and tevuah (produce), he is prohibited from consuming these [five species] the words of Rabbi Meir. The sages say: if one has vowed [to abstain] from [consuming] dagan, is prohibited only from [consuming] these [species] only. They are subject to hallah and tithes.