Sforno on Genesis 47:24/ספורנו על בראשית מ״ז:כ״ד

1את האדמה, which is his, והיה בתבואות When it come to the crops, which are his,

2ונתתם חמישית לפרעה, you will hand over one fifth to Pharaoh, for this is what you have to pay him in return for what he has done for you.

3וארבע הידות יהיה לכם לזרע השדה, including the seed which he has to provide for you as any other owner of a field.

4ולאכלכם, and for you to eat, something he is also obligated to provide for his slaves. Considering that he will keep his part of the bargain, he is entitled to keep the remaining fifth for himself.