CC Ādi 17.308
na tāṁs tarkeṇa yojayet
prakṛtibhyaḥ paraṁ yac ca
tad acintyasya lakṣaṇam
acintyāḥ — inconceivable; khalu — certainly; ye — those; bhāvāḥ — subject matters; na — not; tān — them; tarkeṇa — by argument; yojayet — one may understand; prakṛtibhyaḥ — to material nature; param — transcendental; yat — that which; ca — and; tat — that; acintyasya — of the inconceivable; lakṣaṇam — a symptom.
“Anything transcendental to material nature is called inconceivable, whereas arguments are all mundane. Since mundane arguments cannot touch transcendental subject matters, one should not try to understand transcendental subjects through mundane arguments.”
This verse from the Mahābhārata (Bhīṣma-parva 5.22) is also quoted in the Bhakti-rasāmṛta-sindhu (2.5.93), by Śrīla Rūpa Gosvāmī.