Brihadaranyaka Upanishad 2.5.10

2.5.10

ayamākāśaḥ sarveṣāṃ bhūtānāṃ sadhvasyākāśasya sarvāṇi bhūtāni madhū yaścāyamasminnākāśe tejomayo'mṛtamayaḥpuruṣo yaścāyamadhyātmam̐ hṛdyākāśastejomayo'mṛtamayaḥ puruṣo'yameva sa yo'yamātmedamamṛtamidaṃ brahmedam̐ sarvam

This ether is like honey to all beings, and all beings are like honey to this ether. (The same with) the shining, immortal being who is in this ether, and the shining, immortal being who is (identified with) the ether in the heart, in the body. (These four) are but this Self. This (Self-knowledge) is (the means of) immortality; this (underlying unity) is Brahman; this (knowledge of Brahman) is (the means of becoming) all.