To fully understand the significance of the Windows they must be viewed against Chagall's deep sense of identification with the whole of the Jewish history, its tragedies and victories, as well as his own personal background in the shtetl of Vitebsk, where he was born and grew up.
"All the time I was working," he said, "I felt my father and my mother were looking over my shoulder, and behind them were Jews, millions of other vanished Jews of yesterday and a thousand years ago."
The Bible was Chagall's main inspiration, particularly Genesis 49, where Jacob blesses his 12 sons, and Deuteronomy 33, where Moses blesses the Twelve Tribes. The dominant colors used in each window are inspired by those blessings as well as by the description of the breastplate of the High Priest in Exodus 28:15, which was described as gold, blue, purple and scarlet, and contained 12 distinct gems. Each gem was dedicated to a tribe with the tribe's name engraved on it.
You shall make a breastpiece of judgment, in skilled work; you shall make it in the style of the ephod; of gold, of blue and purple and crimson yarns, and of fine twisted linen you shall make it.
It shall be square and double: a span in length and a span in width.
You shall set in it four rows of stones: a row of carnelian, topaz and chrysolite shall be the first row;
and the second row a moonstone, a sapphire and an emerald; and the third row a jacinth, an agate, and an amethyst; and the fourth row a beryl, an onyx, and a jasper; they shall be set in gold filigree.
There shall be twelve stones with names corresponding to the names of the sons of Israel; they shall be like signets, each engraved with its name, for the twelve tribes.
You shall put the two cords of gold in the two rings at the edges of the breastpiece;
the two ends of the two cords you shall attach to the two settings, and so attach it in front to the shoulder-pieces of the ephod.
So Aaron shall bear the names of the sons of Israel in the breastpiece of judgment on his heart when he goes into the holy place, for a continual remembrance before the Lord.
In the breastpiece of judgment you shall put the Urim and the Thummim, and they shall be on Aaron's heart when he goes in before the LORD; thus Aaron shall bear the judgment of the Israelites on his heart before the Lord continually.
The Symbolic Background of the Windows
The 12 tribes are the descendants of the 12 sons of the Patriarch Jacob, (later named Israel). Jacob had two wives: his beloved Rachel and her elder sister Lea. He also had children by Bilhah and Zilpah, the two handmaids of his wives. Jacob considered Rachel his only wife. He said to his sons: "You know that there are two born to me by My Wife..."
Although he loved Rachel, his cunning, evil father-in-law and uncle tricked him into marrying Lea. The two handmaids were offered to Jacob by his wives when they were unsatisfied with their own fertility. This was in full accordance with the habits and the written laws of that generation. The right of a wife to offer her handmaid to her husband and the status of the offspring are fully discussed in the code of Hammurabi.
According to the Bible, each of the tribes had its own flag and emblem, as cited in Numbers: 2, 2:
"The sons of Israel shall encamp, each by his flag, with the emblems of their fathers' house."
The background of the flag was said to be based on the color of the corresponding gem on the breastplate. The tribal emblems were based mainly on the texts of the Jacob's blessings to his sons (Genesis 49) and Moses' blessings to the tribes (Deuteronomy 33).