Laws of Cricket 1947 Code - Law 30
If the ball, not having been called "Wide" or "No Ball", pass the Striker without touching his bat or person, and any runs be obtained, the Umpire shall call or signal "Bye"; but if the ball touch any part of the Striker's dress or person except his hand, and any run be obtained, the Umpire shall call or signal "Leg Bye"; such runs to be scored "Byes" and "Leg Byes" respectively.
Notes on Law 30
1. If the striker wilfully deflects the ball with any part of his person, no runs are scored, and the batsmen may not change ends.
2. The umpire signals "Bye" by raising an open hand above the head, and "Leg Bye" by raising a leg and touching it with the hand.
Reproduction of the Laws of Cricket is by kind permission of Marylebone Cricket Club