Yama, while instructing Naciketa describes the eternal Asvattha tree with its root upwards, and branches downwards, which is the pure immortal Brahman, in which all these worlds are situated, and beyond which there is nothing else (Katha Upanishad Verse II.iii.1).
Yama, instructing Naciketa, describes the eternal Asvattha tree with its root directed upwards and branches stretching downwards, representing the supreme, ageless Brahman that contains all existence and surpasses anything else (Katha Upanishad Verse II.iii.1).