Is this proverb, "Tell me who your friends are and I will tell you who you are," a declarative or an imperative sentence? What are the reasons for your answer?
I would say imperative.
Imperatives are commands. The person is commanding the other to tell him/her something.
If it were a declarative sentence, it would simply be stating something, not ordering another to do something.
Example of declarative sentence:
You told me who your friends are. In this sentence, the person is simply saying that you told him/her who your friends are, not for you to tell him/her anything.
Example of imperative sentence:
Call me as soon as you get back. In this sentence, the person is telling the other to call him/her. He/she is not suggesting, he/she is not stating that the other has called him/her or that he/she wants the other to call him/her. The person is telling/demanding the other to call.