Q: What I am wondering is ... what is the Hindu equivalent of the 10 commandments? I mean, what code, book or document do Hindus refer to, when they are deciding that such and such is a wrong or right moral action? Thanks
A: There is no equivalent set of laws for Hindus (e.g. the 10 absolutes for all Hindus). Though there are many codes and obligations, indeed thousands of them in Hinduism, there is not one clear delineated set that is binding on all Hindus. Indeed there are at times contradictory principles that can seem confusing as Hinduism is a collection of many, many, different religious subsets. Hinduism is more like a collage of different paths and ways, united by a few general concepts. The Vedas are the oldest writings and are generally recognized as the most authoritative writings, but often the more recent and popular writings (e.g. Puranas) are more known and have more sway among Hindus. The Laws of Manu are examples of very specific and detailed rules for living.
Indeed, you can even have different practices and ethics based upon the different paths of Hinduism. The different ethics and options within Hinduism can present a bewildering array to many people. There is the way of works, the way of contemplation, the way of devotion, and the way of reason, -- each for the different types of people. These are called “Karma-yoga” (action), “Jnana-yoga” (contemplation), “Bhakti-yoga” (emotions), and “Raja-yoga” (reason). There is a path of regulation of desires (Pavrittit Marga), there is a path of renunciation (Nivritti Marga) which each have differing specifics and guidelines for spiritual progress. You can find contradictory practices where one group of Hindus tries to renounce and deny their desires (e.g. the ascetic yogi Pantajali), and another group that sets about to fulfill desires (e.g. tantrics).
In Hinduism, truth is a many-layered thing, and just as there are many gods and goddesses, there are many codes and systems by which someone can have a valid spiritual life. It is a worldview which affirms that the many differing paths lead to the same end.
One of the key concepts in Hinduism is that man can progress and improve and reach mukti or enlightenment. You can choose your path to do it and the ethics and rituals of these multiple paths are ways in which men can ascend the heavenly ladder. This is the place of real contrast to the 10 commandments. The 10 commandments were given not as a way to achieve this goal. Though they can certainly serve as a guide of what to do and not to do, they were never given as a way to find salvation or some form of mukti. In fact it is somewhat the opposite. The Bible teaches that the law was given to instruct and teach people that they couldn’t keep the law—that there is something essentially wrong with man in his heart. The New Testament author, Saul of Tarsus, makes this point-- that those who try to keep the law will find that they can’t and are judged by it (Letter to the Romans, Chapter 2), as well as those who do not know the law—they are also judged by their own standards of their own conscience. Humanity and the law operate like the man who passes by the bench that has the sign, “Wet paint, do not touch!” What does the man do? He stops, reaches out and touches the bench to see if it is wet. The law doesn’t make us better people; the law shows us who we are. All this is to say that the 10 commandments of the Bible are not given as a system to improve humanity. They are given to show us our need. This law then is a preparation for what God will do for man: grace. Man is saved by the grace of God, it is a gift offered by God, it is not something man does by his own works.