Source of both Mantra's
literally meaning Divine-Eternal tales of Supreme God) is one of the maha (prefix meaning great) Puranic texts of Hinduism, with its focus on bhakti (religious devotion) to Supreme God Vishnu (Narayana), primarily focusing on Krishna.
First line of the Kabul manuscript has the earlyest source, the same as the Indus seals. The Mantra from the Bhāgavata Purāṇa
oṁ namo bhagavate vāsudevāya
The mantra also known as the "twelve syllable mantra", which believed to be the earliest mantra from pre-reformation times, pre-dating sectarian divisions in Vaishnavism- (IAST oṁ namo bhagavate vāsudevāya), it is translated as "Om, reverence to the Lord Vāsudeva (Krishna)".