Casting divine spells with shield and weapon

[Palagast]

After tonight's game session, I had a disagreement with one of my friends about casting a divine spell with a somatic component while having both a shield and a weapon in hands. He's under the impression that you can cast a divine spell under such circomstances because the shield only invokes ARCANE spell failure and no divine. I say that regardless, you need one free hand (or perhaps for this matter a shield isn't in your hand but on your arm so you can do it (a buckler works this way at least)) to cast any spell with a somatic component.
Who is right here? I can't find anything in the PHB about it, any reference for this?

Thanks

 

[Hypersmurf]

Divine spells don't suffer from ASF. That doesn't change the fact that you need a free hand to perform a somatic component, or to manipulate M/F/DF components.

With a heavy shield - no way.

Light shields and bucklers are debated.

It's generally agreed that while wearing a buckler, you can perform S components... but some people feel that should deny you the AC bonus of the buckler that round.

Light shields say you can hold an object (such as a torch)... but there is argument as to whether this is sufficiently 'free' a hand to cast a spell.

The accepted method of casting while using a light shield seems to be to use the 'hold an object' clause to shift your mace into your shield hand (free action) while you cast using your now-unambiguously-free weapon hand, then shift the mace back (free action) after you've finished casting.

-Hyp.