You should not copy others.
David is taking an exam in his calculus class that he didn't study for.
David wants to pass the exam.
David takes the exam to the best of his ability and leaves comments to his teacher on the items he doesn't understand.
David copies exam answers from the student sitting next to him.
David's teacher is sympathetic and allows David to retake the exam.
David's teacher catches him cheating and ends up failing David on the exam.