וְעָשִׂ֜יתָ חַ֤ג שָׁבֻעוֹת֙ לַיהוָ֣ה אֱלֹהֶ֔יךָ מִסַּ֛ת נִדְבַ֥ת יָדְךָ֖ אֲשֶׁ֣ר תִּתֵּ֑ן כַּאֲשֶׁ֥ר יְבָרֶכְךָ֖ יְהוָ֥ה אֱלֹהֶֽיךָ׃
И соблюдай праздник недель у Господа, Бога твоего, по меру добровольного приношения руки твоей, которую Ты дашь, как благословит тебя Господь, Бог твой.
Rashi
מסת נדבת ידך means sufficient (די) free-will offerings of thy hand (i.e. of thy possession) (cf. Targum on Deuteronomy 15:8, which renders די מחסרו by כמסת חסרונה); everything must be in accordance with the blessing which God has bestowed upon you (אשר יברכך): offer peace-offerings of rejoicing and invite guests for the meal.
Ibn Ezra
The letter samekh in the word tribute [Hebrew: missat] is vocalized with a dagesh to indicate the absorption of a nun ; the word comes from “flag” [Hebrew: nes], in the sense of “raising up one’s arm”,