The fourth chapter of the twelfth book, or Canto, of the Bhāgavata Purāṇa, also called the Śrīmad Bhāgavatam. It was written by the Vedic sage Śrī Kṛṣṇa Dvaipāyana Vyāsadeva and is about the life and times of Śrī Kṛṣṇa, the most renown avatar of India who spoke the Bhagavad Gītā. Text at: http://bhagavata.org/canto12/chapter4.html