Before the affixes 1. iṣṭha 2. iman and 3. īyas , the ṛ of ṛju may optionally be changed to r , in the chandas (Vedas).,
As रजिष्ठः and ऋजिष्ठः, in रजिष्ठमेति पन्थानम्, त्वमृजिष्ठः ॥,
Adhyāya 6 · Pāda 4 · Rule 162
Before the affixes 1. iṣṭha 2. iman and 3. īyas , the ṛ of ṛju may optionally be changed to r , in the chandas (Vedas).,
As रजिष्ठः and ऋजिष्ठः, in रजिष्ठमेति पन्थानम्, त्वमृजिष्ठः ॥,