Betook himself did Korah, the son of Yitzhar son of Kahas son of Levi, and [so did] Dasan, and Aviram, the sons of Eliav, and On the son of Peles, the children of [the tribe of] Reuven.

Be careful [in your dealings] with the ruling authorities for they do not befriend a person except for their own needs; they seem like friends when it is to their own interest, but they do not stand by a man in the hour of his distress. (Sefaria)

Hillel said, “Do not remove yourself from the community…and do not judge your friend until you have arrived at his place, and do not say a thing that is impossible to hear, that in its end will be heard.

Nittai of Arabel says, “Separate yourself from a bad neighbor; do not befriend the rasha, and do not despair from the calamity.”

And thus, the text says, "He who walketh with wise men shall be wise: but the companion of fools shall be broken" (Prov. 13:20). || "He who walketh with wise men shall be wise." To what is this like? To one who enters a perfumer's shop, although he neither takes anything nor gives anything, nevertheless he absorbs a good scent, and goes away (therewith). Likewise, everyone who walks with the righteous acquires some of their good ways and deeds. Therefore, it is said, "He who walketh with wise men shall be wise." "But the companion of fools shall be broken" (ibid.). To what is this comparable? To a man who enters a tannery, although he neither takes nor gives anything, nevertheless he has absorbed a foul odor. Likewise, he who walks with the wicked acquires some of their evil ways and deeds, which is according to what is written, "But the companion of fools shall be broken" (ibid.). (Sefaria, but I did the bolding)