Chandogya Upanishad 5.16

atha hovāca buḍilam āśvatarāśvim vaiyāghrapadya kaṃ tvam ātmānam upāssa iti apa eva bhagavo rājann iti hovāca eṣa vai rayir ātmā vaiśvānaro yaṃ tvam ātmānam upāsse tasmāt tvaṃ rayimān puṣṭimān asi

Then he said to Budila Âsvatarâsvi, 'O Vaiyâghrapadya, whom do you meditate on as the Self?' He replied: 'Water only, venerable king.' He said: 'The Self which you meditate on is the Vaisvânara Self, called Rayi (wealth). Therefore are you wealthy and flourishing.

atsy annaṃ paśyasi priyam atty annaṃ paśyati priyaṃ bhavaty asya brahmavarcasaṃ kule ya etam evam ātmānaṃ vaiśvānaram upāste bastis tv eṣa ātmana iti hovāca bastis te vyabhetsyad yan māṃ nāgamiṣya iti

'You eat food and see your desire, and whoever thus meditates on that Vaisvânara Self, eats food and sees his desire, and has Vedic glory in his house. 'That, however, is but the bladder of the Self, and your bladder would have burst, if you had not come to me.'