अस्तेर् भूः

भविता 'he will be,' भवितुम् 'in order to be' भवितव्यम् 'must be.' Now the Perfect tense affixes are also ardhadhatuka affixes 3.4.115. The Perfect of अस् is therefore the same as that of भू, namely, बभूव &c. There is, however, an important exception to this rule, namely, when अस् is employed as an auxiliary verb in forming Periphrastic Perfect of other verbs. In that case अस् forms its Perfect tense regularly, आस आसतुः आसुः &c. This apparent breach of the present sutra is explained by taking the term कृञ् in 3.1.40 as a Pratyahara including कृ, भू and अस्, and if अस् could not form its Perfect in the regular way, its inclusion in this Pratyahara would be useless; hence we conclude, that as an auxiliary verb, अस् forms its Perfect regularly.,