Srimad Bhagavata Purana

Mother Yaśodā challenged Kṛṣṇa, “If You have not eaten earth, then open Your mouth wide.” When challenged by His mother in this way, Kṛṣṇa, the son of Nanda Mahārāja and Yaśodā, to exhibit pastimes like a human child, opened His mouth. Although the Supreme Personality of Godhead, Kṛṣṇa, who is full of all opulences, did not disturb His mother’s parental affection, His opulence was automatically displayed, for Kṛṣṇa’s opulence is never lost at any stage, but is manifest at the proper time.