Change the narration: "Be polite to others" I said to him."

I talked him to keep polite to others.

I request him to stay polite to others.

I advised him to be polite to others.

None of these

Direct Speech: "Be polite to others," I said to him.

This is an imperative sentence (a command or advice).

In indirect speech:

Imperative sentences change into infinitive form (to + verb).

"Said to" becomes advised (since it's about good behavior).

So, the correct transformation is:

I advised him to be polite to others.