When ḍh or r are elided, there is the substitution of o or ā of the verbs sah and vah,
Thus सोढा, सोढुम्, सोढव्यम्, वोढा, वोढुम् and वोढव्यम् ॥ Why do we say of अ or आ? Observe ऊढः, ऊढवान् ॥ Why do we say अवर्णे which includes long आ also ? The rule will apply even when the short अ of सह and वह is changed to आ by Vriddhi: as उदवोढाम्, उदवोढम् ॥ Had merely अ been read into the sutra, instead of अवर्ण then coming after the त् of ओत्, it would have denoted only short अ (तादपि पर = तपरः 1.1.75).,