Reply To: washing netilas yadayim on shabbos

From Limud Torah Web site: The Maharam did not wipe his hands on a towel until he removed most of the water from them by vigorously flaying his hands. He was worried that an excess of water would result with transgressing the Issur of laundering the towel on Shabbos. The Mechaber concludes that it is a good thing to keep this Chumra. The Rama says there is no reason to keep it, for even if there is some excess water which gets on the towel, it is only done in a manner which will make the towel dirtier.

The Magen Avraham says that the reason why the Mechaber holds this to be a Chumra, is since there is no dirt on the towel, soaking it is not considered laundering. The Tosfos Shabbos asks why in Simon 319 the Mechaber seems to hold that someone must be careful M’Iker Hadin not to soak something even when it does not have dirt on it. So we must conclude the Mechaber holds according to the reasoning of the Rama here, and considers wiping one’s hands on a towel to be dirtying the towel.