तेन तं हायास्य उद्गीथमुपासांचक्र एतमु एवायास्यं मन्यन्त आस्याद्यदयते ॥ १.२.१२ ॥
In plain words
Ayāsya worshipped it as the Udgītha; and men hold this very breath to be Ayāsya, since it goes forth from the mouth.
The commentators
Chāndogyopaniṣadbhāṣyam· bhāṣya
तथा यत् यस्मात् आस्यात् अयते निर्गच्छति तेन आया- स्य ऋषि प्राण एव सन् इत्यर्थ । तथा अन्योऽप्युपासक आत्मानमेव आङ्गिरसादिगुण प्राणमुद्गीथमुपासीतेत्यर्थ ॥
In plain words
And because it issues forth from the mouth, therefore the seer Ayasya is indeed the vital breath itself—this is the meaning. Similarly, any other seeker should meditate upon his own self, endowed with attributes such as being Angirasa, as the vital breath and as the Udgitha.
Close to the Sanskrit
And because from the mouth it goes forth, therefore the seer Ayasya is indeed breath being such, this is the meaning. Likewise any other worshipper should meditate upon his own self as the vital breath possessing qualities like Angiras as the Udgitha, this is the meaning.