Chullin 16 - Slaughter With a Sharpened Reed
A hand sickle had two cutting edges, one smooth like a knife and the other serrated like a saw. If one slaughters with the smooth side of a sickle, his shechitah is valid. If he slaughters with a sharpened piece of flint or with a sharpened reed, his slaughter is also valid.
"If one slaughters" implies that one really should not, but if he did, it is valid. Why? This is the opinion of Rabbi Yehudah the Prince, who invalidates the slaughter done by an implement attached to the ground. If it was detached, and then later reattached, then Rabbi Yehudah asks not to use it, but if it was used anyway, he considers the shechitah valid.
Rabbi Chiya always permits the shechitah done with something that is attached to the ground. Once Rav and Rabbi Chiya were sitting in a lecture of Rabbi Yehudah who said, "How do we know that shechitah must be done with a detached implement? - Because it is written, ' And Abraham took the knife to slaughter his son .'"
Said Rabbi Chiya, "This proof is as full of cracks as a letter vav written on a piece of a tree trunk. Abraham was zealous and brought a knife. But in truth anything sharp on the mountaintop would do."
Art: Caravaggio - The Sacrifice of Isaac