Menahot, Chapter Eleven, Mishnah Seven
This mishnah deals with the ceremony of the showbread, bringing in the new loaves and taking out the old. This would occur once a week on Shabbat. The old bread would lie there for the entire week until new loaves were brought and the old ones were distributed to the priests.
1) There were two tables inside the sanctuary, at the entrance of the Temple, the one of marble and the other of gold.
a) On the table of marble they laid the showbread when it was brought in, and on the table of gold they laid the showbread when it was brought out, since we raise [the status] of what is holy and we dont lower it down.
b) And within [the sanctuary] there was a table of gold on which the showbread lay continually.
2) Four priests entered: two bearing the two rows [of the showbread] in their hands and two bearing the two dishes [of frankincense] in their hands;
a) And four went in before them, two to take away the two rows [of the showbread] and two to take away the two dishes [of frankincense].
b) Those who brought them in stood at the north side facing the south, and those who took them away stood at the south side facing the north.
c) These withdrew [the old] and the others laid down [the new], the handbreadth of the one being by the side of the handbreadth of the other, as it is said, Before me continually (Exodus 25:30).
d) Rabbi Yose says: even if these [first] took away [the old] and the others laid down [the new later on], this too fulfills the requirement of continually.
3) They went out and laid [the old bread] on the table of gold that was in the sanctuary [at its entrance].
a) They then burned the dishes [of frankincense] and the loaves were distributed among the priests.
4) If Yom Kippur fell on a Shabbat the cakes were distributed in the evening.
5) If it fell on a Friday the he-goat of Yom Kippur was eaten in the evening. The Babylonian [priests] used to eat it raw for they were not fastidious.
Section one: There were three tables, two outside of the sanctuary and one within. The showbread was baked on Friday and then placed on a marble table for it to cool down. When the bread that had been within the sanctuary was brought out, it was placed on a gold table to be distributed to the priests. This table had to be of gold, because the bread had been on the gold table all week, inside the sanctuary. Once the bread had been on a golden table, it could no longer be put on a table made of material lesser than gold. The third table was where the showbread lay all week, inside the sanctuary.
Section two: The mishnah now describes the process through which the old showbread was removed and the new showbread was laid on the table. The important issue here is that the golden table within the sanctuary should never be without the bread upon it. Thus, while two priests slide the showbread off of one side, the other two priests place the new showbread on the other side. We can see that this ceremony was done with much pomp and circumstance and probably made a great impression upon those priests who saw it performed.
Rabbi Yose holds that continually does not mean that the table cannot go for even a moment without the showbread. Rather, continually means that the table should not be empty overnight (this is explained in the Talmud).
Section three: Upon bringing the showbread and frankincense out of the sanctuary, they would distribute the bread to the priests and burn the frankincense.
Section four: If Yom Kippur fell on Shabbat, and it was impossible to eat the showbread because of the fast, they would distribute the loaves at night.
Section five: If Yom Kippur fell on Friday, the he-goat (see Numbers 29:11) had to be eaten by the priests that night. The Babylonian priests, meaning the priests who returned to the Land of Israel after the Babylonian exile had strong stomachs and could eat the goat raw. The reason that they had to do this is that it was impossible to cook it on Friday because of Yom Kippur or on Shabbat. Since it had to be eaten that night, there was no other option but to eat it raw (wouldnt that make an interesting break-fast, a lot more exciting than bagels and danish!).
As an interesting aside, the Rambam proves from our Mishnah that in talmudic times, Yom Kippur could fall on Friday. Today, since we have a set calendar, Yom Kippur can no longer fall on Friday or on Sunday, although it can fall on Shabbat.