The augment ṣuk is added to the root bhī before the affix ṇi when fear is caused immediately owing to the agent of the Causative.,
As मुण्डो भीषयते, जटिलो भीषयते ॥ See 1.3.68. Herealso भी with long ई being employed in the sutra, indicates that षुक् is added then only, when the root has the form भी, but when it assumes the form भा by (VI. I. 56), the proper augment पुक् will come: as मुण्डो भापयते ॥ Why do we say 'when the agent of the causative is himself the direct cause of fear'? Observe कुञ्चिकयैनं भाययति, for here कुञ्चिका causes fear and not the agent of the verb. The ई is vriddhied and आय substituted.,