וַיֹּ֤אמֶר יוֹסֵף֙ הָב֣וּ מִקְנֵיכֶ֔ם וְאֶתְּנָ֥ה לָכֶ֖ם בְּמִקְנֵיכֶ֑ם אִם־אָפֵ֖ס כָּֽסֶף׃
요셉이 가로되 너희의 짐승을 내라 돈이 진하였은즉 내가 너희의 짐승과 바꾸어 주리라
Haamek Davar on Genesis
If there is no more money. He did not believe them, so he told them to bring their livestock as a test, knowing they would rather part with money than their animals.