OBR
Rule 8.01( Comment: With no runners on base, the pitcher is not required to come to a complete stop when using the Set Position. If, however, in the umpire’s judgment, a pitcher delivers the ball in a deliberate effort to catch the batter off guard, this delivery shall be deemed a quick pitch, for which the penalty is a ball. See Rule 8.05(e) Comment.
(e) The pitcher makes an illegal pitch;
Rule 8.05(e) Comment: A quick pitch is an illegal pitch. Umpires will judge a quick pitch as one delivered before the batter is reasonably set in the batter’s box. With runners on base the penalty is a balk; with no runners on base, it is a ball. The quick pitch is dangerous and should not be permitted.