तदैक्षत बहु स्यां प्रजायेयेति
The Shruti statement is mentioned in Chandogya Upanishad 6.2.3
In this statement Uddalaka Aruni (उद्दालक आरुणि) is explaining to his son Shvetaketu (श्वेतकेतु), the sequence and the source of creation.
Aruni says to his son Shvetaketu that “Sat who is the conscious being, and he thought to create this world, so he made himself into many other elements (fire, water, earth) who finally created this world”
तदैक्षत बहु स्यां प्रजायेयेति – Complete Shruti
तदैक्षत बहु स्यां प्रजायेयेति तत्तेजोऽसृजत तत्तेज ऐक्षत बहु स्यां प्रजायेयेति तदपोऽसृजत । तस्माद्यत्र क्वच शोचति स्वेदते वा पुरुषस्तेजस एव तदध्यापो जायन्ते ॥ ३ ॥
“It (Sat or Brahman) thought, may I become many. Having thought that way it created fire. Than the fire thought, “May I become many’ and it created water. because of the same, whenever a person is in sorrow or grieve, sweat is produced, at that time fire creates water.
Sat or Brahman is the cause and material for this creation. Sat means consciousness.