וְהָיָה֙ בַּתְּבוּאֹ֔ת וּנְתַתֶּ֥ם חֲמִישִׁ֖ית לְפַרְעֹ֑ה וְאַרְבַּ֣ע הַיָּדֹ֡ת יִהְיֶ֣ה לָכֶם֩ לְזֶ֨רַע הַשָּׂדֶ֧ה וּֽלְאָכְלְכֶ֛ם וְלַאֲשֶׁ֥ר בְּבָתֵּיכֶ֖ם וְלֶאֱכֹ֥ל לְטַפְּכֶֽם׃
Ad ogni ricolto darete la quinta parte a Faraone; e le altre quattro parti saranno vostre, per la seminagione della campagna, pel vostro mantenimento, per quelli che avete in casa, e pel mantenimento della vostra figliuolanza.
Rashi on Genesis
לזרע השדה FOR SEED OF THE FIELD — for sowing every year),
Sforno on Genesis
את האדמה, which is his, והיה בתבואות When it come to the crops, which are his,
Or HaChaim on Genesis
חמישית לפרעה, one fifth for Pharaoh, etc. Joseph was astute enough to say that Pharaoh would collect the first 20% of any seed. Even if, as a result, the remaining 80% would be only sufficient for the farmer to plant and to break even, Pharaoh would not agree to collect less than his 20%. On the other hand, the farmers would be at liberty to collect the overage whether there be a lot or a little.