If one chants the holy name of God, Hare Kṛṣṇa mantra," yathā harer nāma-padair udāhṛtaiḥ, padaiḥ, "once, once only, Kṛṣṇa, Rāma, Nārāyaṇa . . ." So harer nāma, not other name, only harer nāma. Yathā harer nāma-padair udāhṛtaiḥ. "Simply once chanting." Uttamaśloka-guṇopalambhakam. The purification of chanting harer nāma (CC Adi 17.21) means as soon as you chant the holy name of Kṛṣṇa, immediately you will see the form of Kṛṣṇa, you will realize the qualities of Kṛṣṇa, you will immediately remember the pastimes of Kṛṣṇa. That is pure chanting of Hare Kṛṣṇa mantra.
That is the commented by Śrīla Jīva Gosvāmī, that a pure devotee who chants Hare Kṛṣṇa mantra, immediately all these—nāma, rūpa, guṇa, līlā, parikara, vasiṣṭha . . . simply by chanting name you will feel the form of Kṛṣṇa: "Here is Kṛṣṇa." Nāma, rūpa, guṇa: "Here are the qualities. Oh, Kṛṣṇa is so qualified. He is so kind. He is so magnanimous." So many qualities you will remember. Nāma, rūpa, guṇa, līlā: then His pastimes. "Oh, Kṛṣṇa instructed Arjuna. Kṛṣṇa played with His cowherd boys. Kṛṣṇa had very nice talks with the gopīs, with His mother, Yaśodā." These things will be remembered. That is factual perfection of chanting