Rashi on Numbers 22:21/רש"י על במדבר כ״ב:כ״א

1ויחבש את אתנו AND HE SADDLED HIS SHE-ASS — From here we may learn that the hatred one bears for a person makes one disregard the rule imposed upon him by his exalted position, for he, himself, not a servant, did the saddling. The Holy One, blessed be He, said: You wicked man! Their ancestor Abraham has already anticipated you in this, as it is said, (Genesis 22:3) “And Abraham rose up early in the morning and saddled his ass”) (Midrash Tanchuma, Balak 8; cf. Sanhedrin 105b).

2עם שרי מואב [HE WENT] WITH THE PRINCES OF MOAB — his heart alike with their hearts (cf. Midrash Tanchuma, Balak 8).