Menahot, Chapter Eleven, Mishnah Eight
The showbread and frankincense are supposed to be arranged on the table on Shabbat and removed the following Shabbat, when the frankincense is burned. The showbread can be eaten that day and the following night.
Our mishnah discusses cases in which this precise order was not followed, and the consequences.
1) If he arranged the showbread on Shabbat and the dishes [of frankincense] on the day after Shabbat, and burned the dishes [of frankincense] on the [next] Shabbat, it is not valid, and one is not liable over it for piggul, remnant, or uncleanness.
2) If he arranged the bread and the dishes [of frankincense] on Shabbat and burned the dishes of frankincense on the day after Shabbat, it is not valid, and one is not liable over it for piggul, remnant, or uncleanness.
3) If he arranged the bread and the dishes [of frankincense] on the day after Shabbat and burned the dishes [of frankincense] on the [next] Shabbat, it is not valid.
a) What should he do? He should leave it until the following Shabbat, for even if it remains many days on the table there is nothing to this.
Section one: The dishes of frankincense must be left on the showbread for the entire week that the showbread is on the table. So if the priest set up the showbread on Shabbat, as he was supposed to do, but didnt put the dishes of frankincense on the table on Shabbat, but rather the next day, then the bread and the dishes are invalid.
If he later burned the frankincense with the intent of eating the showbread the day after Shabbat, then the loaves are not piggul (see 2:2 concerning piggul of the showbread. Piggul is the status of a sacrifice that was offered with the intent of eating after it should no longer be eaten), since the frankincense was already disqualified by not having been placed on the table at the correct time. Similarly, if he eats the showbread after Shabbat, he is not liable for the transgression of remnant. Finally, if he eats the bread while impure or while it is impure, he is not liable for eating the bread in impurity, because he is only liable for eating valid showbread. In other words, since the showbread was never valid, he is not liable for any of the potential transgressions.
Section two: In this case, he arranged the bread and dishes of frankincense at the correct time, but he didnt burn the frankincense on the following Shabbat, as he was supposed to do. Rather he burned them the day after. This disqualifies the frankincense and the bread, and again he is not liable in this case for any possible transgression of piggul, remnant or eating while impure or while the bread is impure.
Section three: If he arranged the bread and frankincense after Shabbat and then burned the frankincense on the following Shabbat, there is a remedy. What he can do is just leave the bread on the table until the next Shabbat when it will count as that weeks showbread. Leaving it on the table longer than it was supposed to be there (in this case 6 days, and then an entire week) does not disqualify the bread.
I should note that the word invalid is missing in some versions of this section. Indeed it shouldnt be here because this showbread is not necessarily invalid, as we learn in the remainder of the mishnah.