Om Namo Bhagavate Vasudevaya is a principle mantra in the Purana's the Srimad Bhagavatam and is used for an invocation. The translation of the mantra, which begins with OM, is provided by Srila Prabhupada as: O my Lord, Śrī Kṛṣṇa, son of Vasudeva, O all-pervading Personality of Godhead, I offer my respectful obeisances unto You. It is advised to chant this mantra daily and the mantra itself is one of the most ancient mantras.