Imperative in reported speech

I've been told that I should use simple past in reported speech when the direct speech is in simple present such as I **am** the best ~> He said he **was** the best but what happens for imperative mood direct speech

"Mom said dont trust strangers"

Or

"Mom said didn't trust strangers"

I think I should maintain the first form. But I'm not sure. And I'm not even sure this relates to the sentence mood. I need the best choice and a further explaination for this :)

Answer

Mom said, "Don't trust strangers".

When you change an imperative sentence from direct to indirect (reported) speech, you don't change the tense in the reported speech; you keep the present tense. What you should do is that you change the reporting speech into should or to-infinitive clause as follows:

Mom told me that I shouldn't trust strangers or

Mom told me not to trust strangers.