Prabhupada's lecture -Śrīmad-Bhāgavatam 1.8.39 - Los Angeles, May 1, 1973
Every one of us, life after life, we are committing simple sinful activities, knowingly or unknowingly. Knowingly, I may kill one animal. That is sinful certainly. Even we do it unknowingly, that is also sinful. Just like while we are walking on the street, we are killing so many ants, unknowingly. So in our ordinary dealings, while cooking, while taking water, while using pestle and mortar for smashing spices, we are killing so many animals. So unless we remain Kṛṣṇa conscious, we are liable to be punished for all these unknowingly committing sinful activities. Knowingly, of course, you'll be... That's a fact. Unknowingly. Knowingly or unknowingly. Just like fire. A child unknowingly touches the fire. Does it mean that the fire will excuse the child? No.
The nature's law is so strict, so stringent, that there is no question of excuse. In the ordinary law also, ignorance is no excuse for legal obligation. If you go to the court, and if you say, "My lord, I did not know that the result of this action is this, criminal," that is not pleading that you'll be excused. So therefore Kṛṣṇa consciousness must be there. If we actually want to be free from the reaction of sinful life, that we are doing, knowingly or unknowingly, then Kṛṣṇa consciousness must be there. Kṛṣṇa says, ahaṁ tvāṁ sarva-pāpebhyo mokṣayiṣyāmi [Bg. 18.66]. Therefore it is recommended, kīrtanīyaḥ sadā hariḥ [Cc. Ādi 17.31]. Always we have to be engaged in chanting: Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma..., so that Kṛṣṇa will save us. Knowingly we cannot commit any sinful activities. That is one thing. Unknowingly also we cannot do it. Then we'll be liable.