In essence, the messages of both Bhagavad Gita and Uddhava-Gita are similar, but the Uddhava-gita goes a little bit further in the science of God. Lord Krishna instructed Arjuna at the end of Bhagavad-gita to abandon all varieties of religion, to simply surrender to Him and to execute His will only. Arjuna did just as the Lord had instructed. While the Bhagavad-gita is part of the Mahabharata, the Uddhava-gita occurs in the Bhagavata Purana; both epics were composed by Srila Vyasadeva to highlight the glory of Lord Krishna's descents into the world. Though the Uddhava-gita is drawn from the eleventh canto of Srimad