Why do we dip Challah (traditional in salt or sprinkle it on after making the blessing? Why is the knife drawn across the challa before the blessing is made?
The Talmud (Brachos 55a) states that in place of the Bronze Altar, which stood in the Temple courtyard and was able to bring atonement for the nation, our own tables upon which we dine serve that purpose. There are various interpretations of this statement; what comes of it practically is that just as all offerings were brought with salt, so too we must put salt on our tables. Dipping the bread in salt has Kabbalistic origins while sprinkling the bread with salt has no basis (unless you like salty bread).
The reason for starting the cut of bread is in order to expedite the process of cutting the bread once the blessing has been made, thereby minimizing the time interval between the blessing and the eating.
Regards,
R’ Daniel Fleksher