Humans have a moral obligation to help other humans.
He who wishes to preserve his life at others' expense should also, when it is necessary, be ready to give it up for their sake. The Social Contract is certainly quite problematic by today's standards in that it asserts that the individual must follow the orders of his prince, etc. However, at the time it was important in recognizing that both the leaders and the led have obligations to the other based on their membership within a society. This theory can be generalized to be a part of the relationship between any two individuals. You watch out for me and I'll watch out for you.