Brihadaranyaka Upanishad 5.13.2

5.13.2

yajuḥ prāṇo vaiyajuḥ prāṇe hīmāni sarvāṇi bhūtāni yujyante yujyante hāsmai sarvāṇi bhūtāni śraiṣṭhyāya yajuṣaḥ sāyujyam̐ salokatāṃ jayati ya evaṃ veda

(One should meditate upon the vital force as) the Yajus. The vital force is the Yajus, for all these beings are joined with one another if there is the vital force. All beings are joined for the eminence of him who knows as above, and he achieves union with and abode in the same world as the Yajus (vital force).