आसीनो दूरं व्रजति शयानो याति सर्वतः ।
कस्तं मदामदं देवं मदन्यो ज्ञातुमर्हति ॥ २१ ॥

āsīno dūraṃ vrajati śayāno yāti sarvataḥ |
kastaṃ madāmadaṃ devaṃ madanyo jñātumarhati || 21 ||

21. Sitting, he goes far; lying, he goes everywhere. Who else but me deserves to know the God, who is joyful and joyless.

Shankara’s Commentary:

Otherwise, this atman cannot be known by worldly men having desires, because sitting, i.e., not moving, he goes a great distance. Lying, he goes everywhere. Thus the atman is both joyful and joyless. Thus he has properties mutually opposed; therefore it being impossible to know him, who else but me can know the atman, who is joyful and joyless. It is only by persons like us of subtle intellect and learning that the atman can be known. Being conditioned by conflicting attributes of fixity and movement, and of constancy and change, the atman appears as if itself possessed conflicting attributes like Visvarupa, a sum of various forms, or (more properly) like Chintamani (a gem which appears according to the fancy of the seer). Therefore, Death indicates the difficulty of knowing the atman by the statement ‘who else but me can know the atman.’ The cessation of the activity of the senses is ‘lying;’ in the person lying, there is a cessation of the partial knowledge produced by the senses. In this state the atman seems to go everywhere, because its knowledge then is of a general character, i.e., unqualified by conditions; but, though fixed in its own nature, when it has special or qualified knowledge it seems to go a great distance, because it is conditioned by the motion of the mind and the rest, but really he is here alone, i.e., in this body.