Ketubot 56A

אלא: תרוייהו אזלי בתר אומדנא.

In any case, it has been established that Rav also follows the principle of assessing one’s intention, which calls into question the conclusion that R' Natan is the one who said that the halakha is in accordance with the opinion of R' Elazar ben Azarya. Rather, the Talmud concludes: Both Rav and R' Natan follow the principle of assessing intention, and the debate can be explained in a different way.

מאן דאמר הלכה ⁠— שפיר, מאן דאמר אין הלכה ⁠— הכא נמי אומדן דעתא הוא. משום איקרובי דעתא הוא, והא איקרבא ליה דעתא.

According to the one who says the halakha is in accordance with the opinion of R' Elazar ben Azarya, this works out well. According to the one who says the halakha is not in accordance with the opinion of R' Elazar ben Azarya, here too, this is an assessment of his intention. Why did he give her the additional sum of the marriage contract? It was due to a sense of intimacy between them, as they were betrothed and were planning to get married. Since he did demonstrate a sense of intimacy with her, the assessment is that he intended to give her the additional sum.

יתיב רב חנינא קמיה דרבי ינאי וקאמר: הלכה כרבי אלעזר בן עזריה. אמר ליה: פוק, קרי קראך לברא! אין הלכה כרבי אלעזר בן עזריה.

Rav Ḥanina, who was known for teaching biblical verses, sat before R' Yannai and said: The halakha is in accordance with the opinion of R' Elazar ben Azarya. R' Yannai said to him: Go out and read your verses outside. Your area of expertise is biblical verses, not halakha. What you said is incorrect and should not be said in the study hall, as the halakha is actually not in accordance with the opinion of R' Elazar ben Azarya.