The New Black, Session 4: Mayim Achronim

§ Having mentioned the manner of washing hands during a meal, the Gemara discusses another matter concerning washing hands. Rav Idi bar Avin says that Rav Yitzḥak bar Ashyan says: The first waters, i.e., washing of the hands before eating bread, are a mitzva by rabbinic law, but the final waters, washing of the hands upon conclusion of the meal and before reciting Grace after Meals, are an obligation, a more stringent requirement.

When washing the hands, whether for a meal or for the recital of the Shema or the Amidah prayer, one first says the blessing "Who hast sanctified us by Thy commandments and given us command concerning the washing of the hands". For this is an ordinance of the sages whose instructions the Torah bids us heed, as it is said "According to the law which they shall teach thee' (Deut. 17-11). The washing of the hands after a meal requires no blessing, since it was only instituted as a precautionary measure against danger to health. Special attention should, on this account, be paid to the observance.