In the chandas (Vedas) the substitution takes place diversely.,
That is ऐस् is substituted for भिस् even after stems which do not end in short अ; as नद्यः; and some times the substitution does not take place even after stems ending in short अ, as, देवेभिः सर्वेभिः प्रोक्तम् ॥ देवो देवोभिरागमत् (Rig Veda I. 1. 4).,