Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 117

להיות מקדיש שדהו נותן בערך הקצוב בפרשה, שנאמר: "וְהָיָה עֶרְכְּךָ כְּפִי זַרְעוֹ" (ויקרא כז, טז).

For a person who consecrates his field to give the fixed amount determined by the [Torah], as [Leviticus 27:16] states: "And the value you attach to it shall be according to the amount of seed."