In plain words
He must take care not to listen to bad things. All of these hurt none but himself. That is why we must take care: no bad seeing, no listening to bad words, no bad words, no bad thoughts, no doing of bad deeds.
To act against the conscience: that is what is bad
What is meant by bad? It is simply acting against our conscience. When we act against this conscience, nothing but harm comes to us from it. So this conscience is the form of God within us. Whatever work you do, it decides: this is not right, this is right. But you must take some time for this inquiry of the conscience. There is no room for haste in it. When you want to say something, think a while, inquire "Is it right or wrong, is it good or bad", and only then bring out the word. When you want to listen to something: is this good or bad? Inquiring whether it is right for you or not, you must come to your decision. Not only in what we take in through these five elements: in eating too we must be careful. Eating too much is also hiṃsā. So it is only when you eat in moderation that it brings you ease. So what gives us happiness is Ahiṃsā. What hurts oneself is hiṃsā. Not only that: the water you drink too must be drunk in moderation, in a proper state. In the same way our whole life must be full of Ahiṃsā. When we bathe, many germs die. When we walk, many creatures die. In the work we do, many kinds of germs perish. We need not go so far. Even in the air we breathe, a great many germs perish. All these involve hiṃsā! So, when we want this hiṃsā not to hurt us, if we act in the spirit of ‘All action for the pleasure of God’, this hiṃsā will not hurt us.