Śrīmad-Bhāgavatam · Text 11.17.12
Who is speaking and story frame
त्रेतामुखे महाभाग प्राणान्मे हृदयात्त्रयी ।
विद्या प्रादुरभूत्तस्या अहमासं त्रिवृन्मख: ॥ १२ ॥
tretā-mukhe mahā-bhāga
prāṇān me hṛdayāt trayī
vidyā prādurabhūt tasyā
aham āsaṁ tri-vṛn makhaḥ
O greatly fortunate one, at the beginning of Tretā-yuga Vedic knowledge appeared from My heart, which is the abode of the air of life, in three divisions — as Ṛg, Sāma and Yajur. Then from that knowledge I appeared as threefold sacrifice.
Read the purport on Vedabase.ioFrom Canto 10, chapter 14 onward, the translation and purports were completed by Śrīla Prabhupāda's disciples after his departure, and published by the Bhaktivedanta Book Trust.