For i in mid there is substituted a guṇa before a śit affix.,
As मेद्यति, मेद्यतः, मेद्यन्ति ॥ Why मिद् only? Observe स्विद्यन्ति, क्लिद्यन्ति ॥ The root ञिमिदा belongs both to the Bhvadi and the Divadi classes. The Bhvadi मिद् will get guna before शप् by virtue of 7.3.86, but the Divadi मिद् would not have got guna before श्यन्, as this affix is ङित् 1.2.4: hence the necessity of this sutra. Before non शित् affixes there is no guna, as मिद्यते, मेमिद्यते ॥,