Pitṛgaṇa-Vibhāga (Classification of the Pitṛs) and the Śrāddha–Soma Nourishment Cycle
यज्ञे यस्य पुरा गीता गाथागीतैर्महर्षिभिः / अग्नेर्जन्म तदा दृष्ट्वा शाण्डिल्यस्य महात्मनः
yajñe yasya purā gītā gāthāgītairmaharṣibhiḥ / agnerjanma tadā dṛṣṭvā śāṇḍilyasya mahātmanaḥ
In his sacrifice, long ago, the great Ṛṣis sang hymns in gāthā-songs; then the great-souled Śāṇḍilya beheld the birth of Agni.