Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 155
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 155, with English translation by Maimonides (Rambam).
שלא לאחר הנדרים והנדבות שנדר ושנדב, שנאמר "לא תאחר לשלמו" (דברים כג,כב).
Not to delay bringing sacrifices you have vowed to offer, or animals which you have pledged to bring as sacrifices, as [Deuteronomy 23:22] states: "[When you make a pledge to God,] do not delay paying it."