Mandukya Karika, verse 4.17

Text

फलादुत्पद्यमानस्सन्न ते हेतुः प्रसिध्यति ।
अप्रसिद्धः कथं हेतुः फलमुत्पादयिष्यति ॥ १७ ॥

phalādutpadyamānassanna te hetuḥ prasidhyati |
aprasiddhaḥ kathaṃ hetuḥ phalamutpādayiṣyati || 17 ||

17. Your cause cannot be established if it be produced from the effect. How can the causey which is itself not established, give birth to the effect?

Shankara Bhashya (commentary)

How can there be no causal relation? It is thus replied:—The cause1 cannot have a definite existence if it is to be born of an effect which is, itself, yet unborn, and therefore which is non-existent like the horns of a hare. How2 can the cause contemplated by you, which is, itself, indefinite and which is non-existent like the horns of a hare, produce an effect? Two things which are mutually dependent upon each other for their production and which are like3 the horns of a hare, cannot be related as cause and effect or in4 any other way.