English of Core Text: It was taught: The men of the watch would fast every day; on Monday they would fast for those who set out to sea, [because of that which is said on it] “And God said, Let there be a firmament in the midst of the waters.”
On the daf / in context: The Yerushalmi records the special fasts of the mishmar. Monday’s fast is linked to the second day of creation and the separation of the waters, a moment of danger for seafarers.
Type of Learning: Custom (mishmar fast linked to day of creation)What Is Learned: The second day’s creation of the firmament is the scriptural association for the Monday fast of the mishmar on behalf of seafarers.