Khandogya-Upanishad: Sixth Prapathaka, Eleventh Khanda
1. “If some one were to strike at the root of this large tree here, it would bleed, but live. If he were to strike at its stem, it would bleed, but live. If he were to strike at its top, it would bleed, but live. Pervaded by the living Self that tree stands firm, drinking in its nourishment and rejoicing;
2. “But if the life (the living Self) leaves one of its branches, that branch withers; if it leaves a second, that branch withers; if it leaves a third, that branch withers. If it leaves the whole tree, the whole tree withers. In exactly the same manner, my son, know this.” Thus he spoke:
3. “This (body) indeed withers and dies when the living Self has left it; the living Self dies not.
“That which is that subtile essence, in it all that exists has its self. It is the True. It is the Self, and thou, Svetaketu, art it.”
“Please, Sir, inform me still more,” said the son.
“Be it so, my child,” the father replied.