Vaisesika Sūtra 7.2.07

kāryakāraṇayor ekatvaika-pṛthaktvābhāvād ekatvaika-pṛthaktvaṃ na vidyate ॥7॥

Because of the absence of oneness (ekatva) and oneness-in-difference (ekapṛthaktva) between the cause and the effect, such oneness or oneness-in-difference does not come to light.