Chandogya Upanishad 5.48

तस्मिन्यवात्संपातमुषित्वाथैतमेवाध्वानं पुनर्निवर्तन्ते यथेतमाकाशमाकाशाद्वायुं वायुर्भूत्वा धूमो भवति धूमो भूत्वाभ्रं भवति ॥ ५ ॥

5.10.5 — tasminyavatsampatamushitvathaitamevadhvanam punarnivartante yathetamakashamakashadvayum vayurbhutva dhumo bhavati dhumo bhutvabhram bhavati || 5 ||

After having remained in it as long as there is a residue [of their good works], then by that course by which they came they return again, just as they came, into space; from space, into wind. After having become wind, one becomes smoke. After having become smoke, he becomes mist.

'वहाँ जब तक संपात शेष है, तब तक निवास करके, उसी मार्ग से पुनः लौटते हैं — जैसे आये थे। आकाश में, आकाश से वायु में; वायु होकर धूम बनते हैं; धूम होकर अभ्र बनते हैं।'