פירוש על קידושין 127:16

Rava said that R. Natan believes him in the baraita because he is retracting a statement at the time of his death. However, in other cases, such as that in the mishnah, where he simply makes a statement, R. Natan would not believe him.

Abaye points out that Rava’s statement does not make sense. If he is believed in the case of the baraita where he contradicts his previous words, all the more so he should be believed in the case of the mishnah, where is not contradicting any previous statement.