> we don't know God's will if those jews should live or not,

No, we don't. But I do know that God doesn't want me to sin. That doesn't mean that I can do nothing in that moment to try and protect lives, but I can't sin. 

I can try to talk my way out of it (without lying), I can try to distract to buy time for them to escape, or I can keep my mouth shut and hope their hiding spot is good enough to go undiscovered. But I can't lie. 

We are called to be martyred, but martyrdom is to embrace your fate. Lying in that situation is not embracing your fate. It is lying in an attempt to save yourself and the ones in your home. Had Peter been murdered while he was claiming he didn't know Jesus, that would not be martyrdom.b