Tractate Menachot - Chapter 12 - Mishnah 2 מנחות פרק י״ב משנה ב׳

If one said, “I take upon myself [to bring a minhah prepared] on a griddle”, and he brought one prepared in a pan, or “a minhah prepared in a pan”, and he brought one prepared on a griddle, what he has brought he has brought, but he has not fulfilled his obligation. [But if he said, “I take upon myself] to bring this [flour] as a minhah prepared on a griddle”, and he brought it prepared in a pan; or as “a minhah prepared in a pan”, and he brought it prepared on a griddle, it is invalid. If one said, “I take upon myself to bring two tenths in one vessel”, and he brought them in two vessels, or [he said] “in two vessels,” and he brought them in one vessel, what he has brought he has brought, but he has not fulfilled his obligation. But [if he said, “I take upon myself to bring] these [two tenths] in one vessel”, and he brought them in two vessels, or “in two vessels”, and he brought them in one vessel, they are invalid. If he said, “I take upon myself to bring two tenths in one vessel” and he brought them in two vessels, and when they said to him, “You vowed to bring them in one vessel”, if he brought them in one vessel, they are valid, but if he still offered them in two vessels, they are invalid. If he said “I take upon myself to bring two tenths in two vessels”, and he brought them in one vessel, and when they said to him, “You vowed to bring them in two vessels”, if he offered them in two vessels they are valid; but if he still kept them in one vessel, they are considered as two menahot which have been mixed.