What is the meaning of the bread as portrayed in Leviticus 24:5-8? What does this represent?
In Judaism, God rested on the Sabbath.1 In order to observe the Sabbath, challah bread is made with three or six strands, though there seems to be no obligation to make three-strand challahs or six-strands challahs. The six-strand challah may represent a sense of unity, as Shabbat (Jewish Sabbath) represents a sense of unity, bringing all the diversity of Jewish life for a peaceful harmony and unity that only the Shabbat can achieve. Putting two challahs together is thus also symbolic of the twelve showbreads which were placed every Shabbat on the Table in the Holy Temple sanctuary; each challah represented one of the twelve tribes of Israel. The bread as portrayed in Leviticus 24:5-8 is a depiction of the Sabbath ritual, when there was a Holy Temple in Jerusalem.
What is the purpose of the bread being renewed every Sabbath?
The purpose of the bread, Challah, being renewed every Sabbath is part of a Jewish festival to honor the Lord (YHWH). God rested on the Sabbath; so do his people. The symbolism of the ritual tells the aspirations (living happily under YHWH's rule) and fears (death or exile) of the Jewish people.
In regards to how the Jewish Sabbath relates to contemporary Jewish life, the food preparations are made well in advance, on Friday, and afterwards, a festive meal is held, which is opened by a Kiddush blessing over two whole loaves of bread called Challah. The sumptuous meal, including fish and salads, chicken or meat and other delicacies, is an integral part of the Sabbath. The Jewish Sabbath has been described to represent "the meeting of heaven and earth".2
Source: Trevaskis, Leigh M. "The Purpose Of Leviticus 24 Within Its Literary Context." Vetus Testamentum 59.2 (2009): 295-312. Academic Search Premier. Web. 8 Feb. 2014.
The Symbolic Dimension of Lev 24:1-9 as the Key to Understanding the Unity of Lev 23-25
The Bread (vv. 5-9)
Keeping in mind that the lights of the men̆ ōrāh may represent YHWH’s
presence, and if the twelve loaves of bread represent the tribes of
Israel, it would seem fitting that Moses is responsible for placing
the latter in the symbolic presence of YHWH. Moreover, the role of the
priests in maintaining this relationship is hinted at by the
requirement that Aaron “regularly” arrange the loaves before the Lord
(v. 7).
[I]t seems more likely that the rite concerning the 12 loaves in Lev
24, which requires the addition of frankincense, in combination with
the rite of the men̆ ôrāh, is intended to symbolise the life Israel
was redeemed to live under YHWH’s rule—a life of covenant
faithfulness.
But what are we to make of the priests’ consumption of the bread as a
“food gift” (ʾiššeh) to the Lord (v. 9)? If the priests represent YHWH
to the people, it seems reasonable to speculate that their eating of
the bread completes the symbolic meaning of the rite, namely the
Israelite tribes are pictured as completely given to YHWH.
In conclusion, the symbolic dimension of Lev 24:1-9 may account for
its position between the calendrical concerns of Lev 23 and 25. All of
these passages similarly remind Israel of YHWH’s sovereign rule,
symbolised by Israel’s “lights” calendar (Lev 23, 25; cf. Gen 1:14)
and the “light” of the tabernacle men̆ ôrāh (Lev 24:1-9; cf. Gen
1:14). Collectively, these chapters encourage Israel to remain loyal
to YHWH’s rule, first by her pausing to worship YHWH according to the
times stipulated in Lev 23 and 25, and, second, by the regular
positioning of the 12 loaves of bread under the men̆ ôrāh “light” on
the Sabbath (Lev 24:1-9).
Conclusion: The Purpose of Lev 24 within Lev 23-25
Lev 24 encourages its readers to commit themselves to the faithful
observance of the various days, festivals, and years, stipulated in
Lev 23 and 25. On such occasions the Israelites are to embody the
ideal Israel symbolically presented in Lev 24:1-9 and avoid the fate
of the blasphemer graphically portrayed in Lev 24:10-23. By observing
the prescribed festivals Israel would continue living under YHWH’s
rule and within his presence. That is, the symbolic “ideal Israel”
(Lev 24:1-9) would materialise through adherence to YHWH’s rule.
Within the same analogy, Israel would experience the fate of the
blasphemer (Lev 24:10-23), presumably by death or exile (cf. Lev
26:33, 38), if she rebelled against YHWH.
"And God completed on the seventh day His work that He did, and He abstained on the seventh day from all His work that He did." (Genesis 2:2)
Peli, Pinchas. "Shabbat-A Key To Spiritual Renewal In Israel." Judaism 31.1 (1982): 87. Academic Search Premier. Web. 8 Feb. 2014.