Reference for Shevuot 50:7
הוא מותיב לה והוא מפרק לה לצדדין קתני לא אכלתי לקרבן לא הנחתי למלקות
Granted, according to Samuel who says that in a case which is not applicable in the future he is not liable for the past, therefore the Divine Law removed the oath of testimony from the category of the oath of utterance; but, according to Rab, for what purpose did the Divine Law remove it? - The Rabbis said to Abaye: In order to make him liable for it twice. He [however] replied to them: You cannot say [he is liable] twice, for it has been taught: [When he shall be guilty] in one of these things - for one you make him liable, but you do not make him liable for two. Well then, according to Abaye, for what purpose did the Divine Law remove [the oath of testimony from the category of the oath of utterance in Rab's view]? - [For this purpose:] It has been taught: In all of them it is said, and it was hidden [from him]; but here, it is not said, and it was hidden; in order to make him liable for wilful as for unwitting [transgression]. The Rabbis said to Abaye: Say that for wilful transgression he is liable one; for unwitting, two. - He replied to them: Is that not what I said: [it is written,] in one [of these things] - for one you make him liable, but you do not make him liable for two; and if [it refers to] wilful transgression, are there, then, two? <br>