חוֹלֵ֣ק עִם־גַּ֭נָּב שׂוֹנֵ֣א נַפְשׁ֑וֹ אָלָ֥ה יִ֝שְׁמַ֗ע וְלֹ֣א יַגִּֽיד׃
Whoso is partner with a thief hateth his own soul: He heareth the adjuration and uttereth nothing.
Rashi on Proverbs
he hears an oath that they adjure him, “Did you see so and so who stole so much and so much from me?” And since he shares with him, he does not testify.