Skandapurana 16.207.57

16.207.57

ekaśayyāsanaṃ paktirbhāṇḍapakvānnamiśraṇam ..
yājanādhyāpanaṃ yonistathā ca saha bhojanam ..
navadhā saṃkaraḥ prokto na kartavyo'dhamaiḥ saha .. 57 ..

Sharing a bed or seat, eating in a common line, mixing pots and cooked food, / officiating at sacrifices, teaching, intermarriage, and dining together— / this mixture is declared to be of nine kinds; it must not be done with degraded persons. // 57