2009-10-01 : Safe Passage doesn’t prevent damage that would be dealt to planeswalkers you control.

2009-10-01 : Safe Passage has no effect on damage that’s already been dealt.

2009-10-01 : Safe Passage prevents all damage, not just combat damage, that would be dealt to you and creatures you control this turn.

2009-10-01 : Safe Passage will prevent damage dealt to creatures that weren’t on the battlefield at the time it resolved.