CHĀNDOGYA UPANISHAD · 1.2.7

अथ ह य एवायं मुख्यः प्राणस् तम् उद्गीथम् उपासां चक्रिरे ।
तं हासुरा ऋत्वा विदध्वंसुर् यथाश्मानम् आखणम् ऋत्वा विध्वंसेतैवम् ॥

atha ha ya evāyaṃ mukhyaḥ prāṇas tam udgītham upāsāṃ cakrire ।
taṃ hāsurā ṛtvā vidadhvaṃsur yathāśmānam ākhaṇam ṛtvā vidhvaṃsetaivam ॥

Then comes this breath (of life) in the mouth. They meditated on the udgîtha (Om) as that breath. When the Asuras came to it, they were scattered, as (a ball of earth) would be scattered when hitting a solid stone.