Finnish translation? Not just an online translator, please?

I want to know the actual Finnish translation of 'what does not kill, strengthens'. I saw it a while back in an article with Jukka Hilden, but can't find the article and so I don't know the actual translation. I want to get it tattooed, so please do not just go to an online translator...I've tried that and got many different things. I appreciate your help! :)