Brihadaranyaka Upanishad 1.30

एतं ह वावसिष्ठं वेद — वसिष्ठः स्वानां भवति — प्राणो ह वावसिष्ठः ॥

etam ha vav vasishthham veda — vasishthah svanam bhavati — prano ha vav vasishthah ||

He who knows Prana as the most excellent (vasishtha) becomes the most excellent among his own people. Prana is truly the most excellent.

जो इसे वसिष्ठ जानता है, वह अपनों में वसिष्ठ (सर्वश्रेष्ठ) बनता है। प्राण ही वसिष्ठ है।