The rule states that a player will be penalised for deliberately knocking on or passing forward. This does not mean it will be a penalty, which is what I think the OP wanted to know. He will be penalised by way of a scrum with head and feed to the opposition.
In terms of a penalty, one CAN be given for a forward pass:
Quote deliberate knock onPenalty for some forward passes
If the Referee is of the opinion that a player in giving a forward pass must have been well aware that the catcher was in front of him then the referee is justified in ruling that the ball has been deliberately thrown forward.'"
(my emphasis)
But other than that, he would normally just be penalised by a scrum.
Quote deliberate knock onScrum for Forward Pass
A forward pass in a passing movement is invariably caused
by misjudgment and is rarely a deliberate offence. Play is
restarted with a scrum after an accidental infringement.'"
So why the reference to a "deliberate knock on", you may ask? Quite easy. Though only understood by experts and select aardvarks. The reason is this:
nearly all knock-ons are deemed accidental, but all knock ons are defined thus:
Quote deliberate knock onKNOCK-ON means to knock the ball towards the opponents’ dead
ball line with hand or arm, while playing at the ball.'"
Most people think it is only a knock on if the ball touches the ground or an opponent, or the sticks. Not so. Generally true, but not if you knock the ball forward deliberately - for example, over the head of a defender - and run round him and catch it at the other side.
The judgment for the ref to make, for example in an intercept situation, is whether the intercepting player tried to catch the ball, or whether he deliberately knocked it on, juggled with it and caught it. I would suggest that the fact penalties for deliberate knock ons are rarely if ever given is it is hard to make a call that a player meant to knock on, when catching the ball would be a great advantage, and so officials presume that must have been the player's intention, however optimistic.
But in theory, it could be given. I expect the next one you'll see given will be against the Bulls in the last minute of some key game. But that could be my bias.