וַיִּגְדַּ֖ל הָאִ֑ישׁ וַיֵּ֤לֶךְ הָלוֹךְ֙ וְגָדֵ֔ל עַ֥ד כִּֽי־גָדַ֖ל מְאֹֽד׃
這人就昌大起來，日益興旺，直到成了極其昌大的人。
Rashi
כי גדל מאד UNTIL HE BECAME VERY GREAT — so that people used to say, “Rather the dung of Isaac’s mules than all Abimelech’s gold and silver’’(Genesis Rabbah 64:7).
Siftei Chakhamim
So that people would say: Rather the dung of Yitzchok’s mules... Otherwise why does it say, “Until he became very great”? [The next verse details his wealth! Perforce,] it comes to tell us the extent [of his blessing]. Thus Rashi mentions mules, since mules [ordinarily] have no blessing at all, as Rashi explained in Devarim 15:14.