וְאִם־גָּאֹ֤ל יִגְאַל֙ אֶת־הַשָּׂדֶ֔ה הַמַּקְדִּ֖ישׁ אֹת֑וֹ וְ֠יָסַף חֲמִשִׁ֧ית כֶּֽסֶף־עֶרְכְּךָ֛ עָלָ֖יו וְקָ֥ם לֽוֹ׃
Rashi on Leviticus
ואם גאל יגאל AND IF HE WILL IN ANY WAY REDEEM IT “he” means, the man who dedicated it; then he shall add a fifth part to this fixed price (not a fifth of the fifty shekels, but a fifth of the value determined by this calculation is to be added to that value).