When are unintended double hits by one player illegal?
Generally, a player contacting a ball (e.g., bumping, passing, setting, hitting, etc.) may make only one contact. However, if the ball touches various parts of the body at the same time (i.e., simultanously), it is NOT a fault. Also, if a player is the first to play the hard-hit ball on his side (e.g., receiving a serve or spike, after a tip off the block, etc.), accidential multiple touches are NOT a foul. Here are the rules: 14.4.3 CHARACTERISTICS OF THE HIT: The ball may touch various parts of the body, provided that the contacts take place simultaneously. EXCEPTIONS: 14.4.3.1 [blocking] AND 14.4.3.2: During the first hit of the team (not blocking) [Rule 19.2], the ball may contact various parts of the body consecutively, provided that the contacts occur during one action. COMMENTARY: The first hit of the team includes receptions: (a) of the serve; (b) of an attack-hit by the opponent [this may be a soft or hard attack-hit]; (c) of a ball blocked by one’s own team and (d) of a ball
