Abarim Publications' online Biblical Hebrew Dictionary
שאר
Scholars insist that there are two distinct roots שׁאר (sha'ar) and one שׂאר (s'r), but although any relationship between these three may not be immediately obvious to some, keep in mind that until the Masoretes added their symbols to the Hebrew texts in the Middle Ages, the following words were indistinguishable:
שׁאר I
The verb שאר (sha'ar I) means to remain, left over or left behind. HAW Theological Wordbook of the Old Testament reports that "sha'ar seems to be used almost exclusively to indicate the static action of surviving after an elimination process" (Exodus 10:19, Ruth 1:3, 1 Samuel 9:24).
This verb comes with some obvious derivatives:
- The masculine noun שאר (she'ar), meaning rest, residue or remnant (Isaiah 10:19, 1 Chronicles 11:8).
- The feminine noun שארית (she'erit), meaning remnant or remainder (Isaiah 44:17, Genesis 45:7).
שׁאר II
Root שאר (sha'ar II) is assumed to have existed because of the common noun שאר (she'er), meaning flesh, and the trouble most scholars appear to have with connecting flesh to a verb that means to remain. The obvious solution is that a person secretes less than he consumes for the obvious fact that some of what he eats builds up his body. A person's body is what stays behind.
Our word occurs to mean flesh for consumption (Exodus 21:10), and as symbol of physical power (Psalm 78:20). But it also occurs to indicate a blood-relation (surviving in our expression "one's own flesh and blood" - Leviticus 18:12). In Proverbs 11:17 this word is used to mean self or one's self.
Note that the noun בשר (basar), the more common word for flesh, comes from the verb בשר (basar), to bring glad tidings, even tidings of comfort and joy.
שׂאר
The meaning of root שאר (s'r) is formally unknown, and only one derivation remains in the Bible: the masculine noun שאר (se'or), meaning leaven (Exodus 12:15, 12:19 and 13:7, Leviticus 2:11 and Deuteronomy 16:4 only). Bread, or anything else, that had leaven in it was called חמץ (hames) and the famous unleavened bread of Passover was called מצה (massa).
Leaven in the Bible
Leaven is a fungus that freely flows through the air and settles on everything, like living dust. It feeds on sugars and produces carbon dioxide, which explains bubbles in bread and beer. Archeology shows that leaven was domesticated thousands of years ago, when people managed to isolate and cultivate strands of leaven that resulted in the best beer and bread. The key to the process was to not use all the leavened dough for bread, but to leave some behind. That remnant or residue was then injected into the next batch of dough, and in time this next batch would have become fully permeated by the original leaven.
The word for bread (לחם, lehem) was also used to denote food in general, and even all things that sustain a person or even a society. The smallest trace of leaven will eventually find its way through the whole batch of dough, and produces a gas (רוח, ruah, meaning wind or spirit) which makes the bread more tasty and easier to eat and digest. Hence leaven acquired the strong symbolic meaning of what we today would call a fad or fashion, or even a "going viral": a full-fledged movement of passion (whether joyous or riotous) that grew out of a relatively small concept and pervades the whole of society.
There's nothing intrinsically bad about this social leaven; it just happens to be the way our world works. Life without social leaven would be boring and not very effective, but, as with any kind of fast track, sometimes things go wrong and the wrong kind of info creeps in (smoking is cool, adultery is fun, etcetera). In that case it's sometimes best to condemn the whole strand of leaven, and start all over with a fresh batch. That's obviously what the Hebrews did when they left Egypt (Exodus 12:8), but it's also what Descartes attempted when he reduced all knowledge to his famous cogito ergo sum.
Jesus compared the evangel to leaven; it starts out as a simple message of love and forgiveness but spreads through the world like leaven through dough, until it forms into a universal and spiritual kingdom (Matthew 13:33). Unfortunately, humans like bad news much more than good news and most of the winds that blow our world are negative (nearly all of the violence we believe in comes from our television; the real world outside our windows is nearly entirely at peace). Hence Jesus warned his audience for the leaven of Herod and that of the Pharisees (Mark 8:15), and Paul warned for the leaven of misinformation (Galatians 5:9).
Paul further spoke of the leaven of boasting and arrogance (1 Corinthians 5:6) and explained that the old leaven must be cleaned out and a start must be made with a new, unleavened lump, "just as you are in fact unleavened. For Christ our Passover also has been sacrificed. Therefore let us keep the [Passover-] Feast, not with the old leaven, the leaven of malice and wickedness, but with bread without leaven, the bread of sincerity and truth" (1 Corinthians 5:7-8).
After all, knowledge puffs up (φυσιοω, phusioo), but love builds up (1 Corinthians 8:1); knowledge is the gas, love is the bread.