Mahabharata 12.321.5

भीष्म उवाच · bhīṣma uvāca

गूढं मां प्रश्नवित्प्रश्नं पृच्छसे त्वमिहानघन ह्येष तर्कया शक्यो वक्तुं वर्षशतैरपि

gūḍhaṃ māṃ praśnavitpraśnaṃ pṛcchase tvamihānaghana hyeṣa tarkayā śakyo vaktuṃ varṣaśatairapi

Our plain-language meaning of this verse is waiting for scholar review.