Netilas Yadayim - Revi'is Measurement

QUESTION: What is the volume of a revi’is? 

ANSWER: A revi’is is equal to 1½ eggs. However, this leads to the next question: how large is a k’beitza (halachic egg)? This is a matter of great dispute. Rav Chaim Naah and many others have calculated that a beitza is about 2 fluid ounces. According to this calculation a revi’is is about 3 oz. However, according to the calculation of R. Yechezkel Landau (Tzlach - Pesachim 109) a revi’is is about 5 oz. The Mishnah Berurah (Beiur Halacha 271:13 s.v. Shel) offers the following recommendation. When we are dealing with an obligation which has a basis in the Torah, such as reciting kiddush on Friday night, we should use the larger measurement of the Tzlach (approx. 5 oz). However, when we are measuring for mitzvos derabbanan, such as netilas yadayim, one may use the smaller measurement of a revi’is (approx. 3 oz), or preferably a compromise amount of about 4 oz.

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The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.