Shloka 54
Saṃhāra-krama (The Sequence of Cosmic Dissolution) — Yājñavalkya’s Discourse
सुस्थेयं क्षुधधारासु निशितासु महीपते । धारणासु तु योगस्य दुःस्थेयमकृतात्मभि:
su-stheyaṁ kṣudhā-dhārāsu niśitāsu mahīpate | dhāraṇāsu tu yogasya duḥstheyam akṛtātmabhiḥ pṛthvīpate ||
ビーシュマは言った。「王よ、刃の鋭い縁の上にさえ人は安らかに立てよう。だが、内なる自己が磨かれず、節制を欠く者にとって、ヨーガのダーラナー（dhāraṇā、心を一点に保つ修習）に堅くとどまることは、まことに至難である。」
भीष्म उवाच
Educational Q&A
External hardships can be borne, but true steadiness in yogic concentration demands an inwardly purified, disciplined mind; without self-mastery (kṛtātman), dhāraṇā becomes extremely difficult.
In the Śānti Parva’s instruction to the king, Bhīṣma emphasizes the rigor of inner spiritual practice, using the razor-edge image to contrast physical endurance with the greater challenge of mental and ethical self-discipline required for yoga.