CC Madhya 25.199

eka ‘nāmābhāse’ tomāra pāpa-doṣa yābe
āra ‘nāma’ la-ite kṛṣṇa-caraṇa pāibe
Word for word: 
eka — one; nāma-ābhāse — by a reflection of the pure chanting of the Hare Kṛṣṇa mahā-mantra; tomāra — your; pāpa-doṣa yābe — all the sinful reactions will go away; āra — then again; nāma la-ite — after chanting purely the name of the Lord; kṛṣṇa-caraṇa pāibe — you will get shelter at the lotus feet of Kṛṣṇa.
Translation: 
Śrī Caitanya Mahāprabhu further advised Subuddhi Rāya: “Begin chanting the Hare Kṛṣṇa mantra, and when your chanting is almost pure, all your sinful reactions will go away. After you chant perfectly, you will get shelter at the lotus feet of Kṛṣṇa.
Purport: 

The ten kinds of offenses should be considered. In the beginning, when one is initiated into the chanting of the Hare Kṛṣṇa mahā-mantra, there are naturally many offenses. Therefore the devotee should very carefully try to avoid these offenses and chant purely. This does not mean that the Hare Kṛṣṇa mahā-mantra is sometimes pure and sometimes impure. Rather, the chanter is impure due to material contamination. He has to purify himself so that the holy names will be perfectly effective. Chanting the holy name of the Lord inoffensively will help one get immediate shelter at Kṛṣṇa’s lotus feet. This means that by chanting purely, one will immediately be situated on the transcendental platform. We should note, however, that according to Śrī Caitanya Mahāprabhu’s instructions, one should not wait to purify himself before chanting the Hare Kṛṣṇa mantra. Whatever our condition may be, we should begin chanting immediately. By the power of the Hare Kṛṣṇa mantra, we will gradually be relieved from all material contamination and will get shelter at the lotus feet of Kṛṣṇa, the ultimate goal of life.