Vedic Metre in its Historical Development c12.s3.46

c12.s3.46

(ii) On the other hand a short vowel is regular before *-vant*, unless the prior element contains itself a long vowel, as is the case in words like *távant*, *svadhávant*, *pátnīvant*, *viṣūvánt*, and even in *aṣṭhīvánt* from *asthán*.