Bhashya
तथा विद्युत्, त्वक्तेजसि भवः तैजसः अध्यात्मम् ॥
In plain words
It is the same with lightning: within you, its counterpart is the heat born in your own skin.
Close to the Sanskrit
So too the lightning: that which is born in the fire of the skin, the fiery one, with reference to the self.