The sārvadhātuka affix se (the ending of the 2nd person Present and Imperative ātmanepadi) get the augment iṭ after the root īśa - adādigaṇaḥ (2nd Conjugation).,
As ईशिषे and इशिश्व ॥ से becomes स्व by 3.4.91 and 3.4.80. The से is exhibited in the sutra without any case-ending.,