Manava Dharmashastra 11.181

11.181

yo yena patitenaiṣāṃ saṃsargaṃ yāti mānavaḥ
sa tasyaiva vrataṃ kuryāt tatsaṃsargaviśuddhaye //

He who associates with an outcast, himself becomes an outcast after a year, not by sacrificing for him, teaching him, or forming a matrimonial alliance with him, but by using the same carriage or seat, or by eating with him.