illegal forward pass

[ggk]

eagles giants game. manning was called for an illegal forward pass. this was challenged and overturned. al michaels quoted a rule that stated that all parts of the passers body must have crossed the line of scrimmage when the ball is thrown for it to be illegal. replay showed that manning's heel was on the line when he released the ball. the ball and the rest of his body was well past the line. is this the correct rule?? is this a newer rule. i thought it might be the location of his feet or the ball. i'm not a football official, so please help. is there a rule citation ? thanks.