Most religions have some concept of sin and various acts and thoughts that are considered sin.  Some of them, such as murder, are common to almost all religions, while others are limited to only to one faith.  So what is sin really?
    Sin is not violating human laws, but violation the laws of God or offending God.  To the enlightened, their is really only one sin and that is ignorance of God and God's Plan.  The reason for saying that is because if you really know God, have actually experienced oneness with God, even very briefly, you will understand what you should do and how to follow God's will to complete God's plan.  If you are ignorant of God, you can't understand His plan and therefore can't dedicate yourself to accomplishing it.  You can, of course, make a promise that you will do your best to learn of God (through enlightenment, not being told what God is and what God wants by priests and minsters) and to follow God's plan.  Until you do become enlightened, you can help to the best of your ability by working with someone who is enlightened.