Powtórzonego Prawa 23:23 Halacha: Mishneh Torah, Positive Mitzvot & Shulchan Arukh, Yoreh De'ah

That a man should fulfill whatever he has uttered, whether in regard to an offering or to charity, and so forth, as it is said, “That which is gone forth out of thy lips, thou shalt keep and perform” (Deut. 23:24).

One who makes the condition: "All vows that I vow until the following time shall be void," and then vows within this time - if they remember the condition at the time of making the vow, then the vow is valid, since the condition is annulled by the vow. If they did not remember the condition at the time of the vow, the condition remains valid and the vow is annulled. There are those who say that the condition cannot annul the vow unless one mentions quickly (toch k'dei dibbur) after the vow that it is being done according to the condition - and one should heed to this opinion.