The affix above ordained is elided by lup after the words 1. śravaṇa and 2. aśvatha when the whole word so formed is an appellation and there is specification of time.,
Thus श्रवणा रात्रिः, अश्वत्थो मुहूर्तः \the night called Sravana; the Muhurta called Asvattha\. The affix being elided by 'lup', why should not 1.2.51 apply here? We should say श्रवणा रात्रिः and not श्चवण रात्रिः The reason is that श्रवणा is an irregularly formed word, as Panini himself uses it in sutra 4.2.23. Why do we say 'when it is a Name or Sanjna'? Observe श्रावणी or आश्वत्थी रात्रिः ।,