Related על תרומות 3:8

[If] he was going to separate terumah at the appropriate time of separation, and he said, "Behold, this is first tithe," then behold, it is first tithe. [If] he was going to separate first tithe at the appropriate time of separation, and he said, "Behold, this is second tithe," then behold, it is second tithe. [If] he was going to separate second tithe at the appropriate time of separation, and he said, "Behold, this is poor person's tithe," behold it is poor person's tithe. [If] he intended to say "second tithe" but he says "poor person's tithe," [or he intended to say] "poor person's tithe" but he says "first tithe," he has not said anything. [If he intended to say] "first tithe" and he said "second tithe," his words are permanent. Rabbi Yosei says, if he intended to separate poor person's tithe [but said "second tithe"], he has not said anything. If instead of "second" [he said] "first," his words are permanent.