minhag - Does one need dry hands before washing?

I've always noticed people that make sure their hands are perfectly dry before washing (i.e. washing for eating bread). Why do people do so? Where does this apparent stringency come from?

Answer

According to the Chazon Ish (Orach Chaim 24:20) they must be completely dry before washing or the washing is invalid b'dieved. According to the Mishna Berura (Beiur Halachah 162:2) they may even be completely wet before washing. The Baal haTanya apparently holds in his Shulchan Aruch like the Mishna Berura but rules in his siddur like the Chazon Ish.