Objective morality

How can morality be objective? After all, the decision whether to apply it comes from the subject. Let’s say that morality comes from the Torah, then it is found (there are moral laws in the Torah). You still need an additional assumption (that you should indeed do what is written in the Torah) for it to become morality. This assumption makes it subjective, doesn’t it? After all, this assumption would not “exist” if there were not people who made it. It does not exist outside of them.