Vaishnava Dharmashastra 26.3

26.3

samānavarṇāyā abhāve tv anantarayaivāpdi ca ||

On failure of a wife of his own caste (he shall perform them) with one belonging to the caste next below his own; so also in cases of distress (i.e. when the wife who is equal in caste to him happens to be absent, or when she has met with a calamity);