badh is the substitute of han 'to kill' when the ārdhadhātuka liṅ (Benedictive) follows.,
वध्यात् 'may he kill,' वध्यास्ताम् 'may they two kill,' वध्यासुः 'may they all kill.'
The substitute वध्, ends with short अ this अ is elided. This elision being like the original (sthanivat 1.1.56), in forming the Aorist, लुङ्, we have अवध् + ० + ईत् = अवधीत्. Here zero being sthanivat prevents the vriddhi of अ of व which otherwise would have take place by 7.2.7.,