The Lord Himself also establishes Himself as the Supreme Personality of Godhead in the Bhagavad-gītā, and He is accepted as such in the Brahma-saṁhitā and all the Purāṇas, especially the Śrīmad-Bhāgavatam, known as the Bhāgavata Purāṇa (kṛṣṇas tu bhagavān svayam (SB 1.3.28)). Therefore we should take Bhagavad-gītā as it is directed by the Personality of Godhead Himself.