Avatarika
सामोपासनप्रसङ्गेन कर्मगुणभूतत्वाभिवर्त्य ओंकार परमात्मप्रतीकत्वादमृतत्वहेतुत्वेन महीकृत्य प्रकृतस्यैव यज्ञस्यअङ्गभूतानि सामहोममन्त्रोत्थानान्युपदिदिक्षन्नाह—
In plain words
In the course of discussing meditation on the Sama chant, the text exalts the syllable Om because it represents the Supreme Self and leads to immortality, serving as an important accessory to ritual action. Wishing now to teach those chants and sacrificial mantras derived from the Sama which form the limbs of the ongoing sacrifice, the scripture says:
Close to the Sanskrit
In the context of meditating on the Sama, having elevated Om—because it is a symbol of the Supreme Self and the cause of immortality, as it serves as an accessory to ritual action—wishing to teach the risings of the Sama oblations and mantras which are limbs of the sacrifice under discussion, he speaks: