The Mishna is Nedarim (10) mentions Moshe Rabeinu’s oath to Yisro to remain in Midyan as a kinuy shevuah. Yet, the gemara later (65a) writes that Moshe was matir neder (aside: I don’t fully understand why the Mishna calls it a shevuah but the gemara treats it as a neder) in order to return to Mitzrayim. The halacha is that hataras nedarim is “okeir haneder m’ikaro”, it uproots the neder and is as if it never existed. If so, asks the Rogatchover, any reference to a shevuah of Moshe should be meaningless!
The Rogatchover derives an important yesod from this question: even though the halachic reality is that the words of Moshe became meaningless, since they are recorded in the Torah they retain eternal validity. There is no such thing as a pasuk which is a hava amina, or a falsehood, in Torah. Simply by virtue of being included in the text, every word becomes eternal truth. (I think this fits nicely with a prior post I did on the existence of the text as an independent construct and not conditional on historical or other considerations.)
The yesod of the Rogatchover is incredible, but perhaps this question on the sugya in Nedarim can be answered differently. R’ Shimon Shkop explains that being okeir haneder does not mean we went back in time and erased the neder, but that we treat the neder going forward as if it never existed. In other words, being okeir a neder does not change the historical reality; it is simply renders consequences that may have emerged from the neder as null and void going forward. When someone uses the “shevu’a of Moshe” as a kinuy, it is the historical reality of the shevuah which is being invoked regardless of the fact that those words were stripped of legal consequence at a later point in time.