Study Guide Eruvin 4 Today's daf is dedicated by Dina Hirshfeld-Becker on her father's second yahrzeit, Alan Hirshfeld, Asher Tuvia ben Shlomo v'Chana z"l. And by Michael Radwin in honor of Ariella Radwin in celebration of their 20th wedding anniversary. And by Yael and Jon Cohen in honor of their son Eddie who drafted yesterday. May Hashem protect you as you do the work that enables our country to be free. עלה והצלח! The gemara brings a tannatic source to question Abaye's understanding of Rav Nachman regarding the size of a cubit (5 or 6 handbreadths). The gemara resolves the issue. The requisite amount, mechitza (separations) and chatzitza (one cannot be purified by a mikveh if there is a separation between the water and one's body) are all oral traditions passed down from Moshe at Sinai. The gemara questions each - aren't they mentioned in the Torah? The gemara explains what is meant by each term in order to answer the question.