Explanation:

- The sentence suggests that someone should not be blamed or held responsible for something they haven't done.

- Option 1: Assure - This means to reassure someone or give them confidence. It doesn't fit in the context of the sentence.

- Option 2: Admit - This means to confess or acknowledge something, often an error or fault. It doesn't align with the given situation where harm is not acknowledged as done.

- Option 3: Accuse - This means to charge someone with a fault or wrongdoing. Given that he has done no harm, it fits perfectly as something you shouldn't do.

- Option 4: Admire - This means to have a high opinion of someone or something. It doesn't relate to the context of having done harm.