Why remove the leaven?
Shemot (Exodus) 12:15-20 For seven days you are to eat bread made without yeast (chametz). On the first day remove the yeast (chametz) from your houses, for whoever eats anything with yeast (chametz) in it from the first day through the seventh must be cut off from Israel. On the first day hold a sacred assembly, and another one on the seventh day. Do no work at all on these days, except to prepare food for everyone to eat–that is all you may do. “Celebrate the Feast of Unleavened Bread, because it was on this very day that I brought your divisions out of Egypt. Celebrate this day as a lasting ordinance for the generations to come. In the first month you are to eat bread made without yeast (chametz), from the evening of the fourteenth day until the evening of the twenty-first day. For seven days no yeast (chametz) is to be found in your houses. And whoever eats anything with yeast (chametz) in it must be cut off from the community of Israel, whether he is an alien or native-born. Eat nothing made with yeast (chametz). Wherever you live, you must eat unleavened bread.”
Shemot (Exodus) 13:6-7 For seven days eat bread made without yeast (chametz) and on the seventh day hold a festival to God. Eat unleavened bread during those seven days; nothing with yeast in it is to be seen among you, nor shall any yeast (chametz) be seen anywhere within your borders.
Removing the leaven of life
In Hebrew, leaven is called se’ whereas a leavened product is called chametz .In ancient times, se’or was as a lump of old dough allowed to reach a high level of fermentation (sometimes called sourdough or yeast). When the piece of sourdough was kneaded together with a mixture of flour and water, it accelerated the rising process and created chametz (today yeast or baking powder function as se’or).
What’s the difference between chametz and se’or? Chametz is food and is edible. You can serve and eat chametz (and often want to!). On the other hand, nobody eats se’or, which is inedible fermented grain which has the function of fermenting other dough.
Chametz is considered a corrupting influence, a hidden uncleanness that manipulates purer elements. Like the influence of a lump of leaven in a batch of dough, “spiritual” leaven functions as an evil impulse within us (i.e., yetzer ra: ) that corrupts and “sours” our soul. This “yeast in the soul” is essentially pride that manifests itself in idolatrous desires and lusts.
1 Corinthians 5:8(ESV) 8 Let us therefore celebrate the festival, not with the old leaven, the leaven of malice and evil, but with the unleavened bread of sincerity and truth.
Removing the leaven of religious pride and Narcissism
Mark 8:14-17 (ESV) 14 Now they had forgotten to bring bread, and they had only one loaf with them in the boat. 15 And he cautioned them, saying, “Watch out; beware of the leaven of the Pharisees and the leaven of Herod.” 16 And they began discussing with one another the fact that they had no bread. 17 And Jesus, aware of this, said to them, “Why are you discussing the fact that you have no bread? Do you not yet perceive or understand? Are your hearts hardened?
Mark 7:1-13 (ESV) 7 Now when the Pharisees gathered to him, with some of the scribes who had come from Jerusalem, 2 they saw that some of his disciples ate with hands that were defiled, that is, unwashed. 3 (For the Pharisees and all the Jews do not eat unless they wash their hands properly,[a] holding to the tradition of the elders,4 and when they come from the marketplace, they do not eat unless they wash.[b] And there are many other traditions that they observe, such as the washing of cups and pots and copper vessels and dining couches.[c]) 5 And the Pharisees and the scribes asked him, “Why do your disciples not walk according to the tradition of the elders, but eat with defiled hands?” 6 And he said to them,“Well did Isaiah prophesy of you hypocrites, as it is written,
“‘This people honors me with their lips,
but their heart is far from me;
7 in vain do they worship me,
teaching as doctrines the commandments of men.’
8 You leave the commandment of God and hold to the tradition of men.”
9 And he said to them, “You have a fine way of rejecting the commandment of God in order to establish your tradition! 10 For Moses said, ‘Honor your father and your mother’; and, ‘Whoever reviles father or mother must surely die.’11 But you say, ‘If a man tells his father or his mother, “Whatever you would have gained from me is Corban”’ (that is, given to God) 12 then you no longer permit him to do anything for his father or mother, 13 thus making void the word of God by your tradition that you have handed down. And many such things you do.”
Mark 6:19-20 (ESV) 19 And Herodias had a grudge against him and wanted to put him to death. But she could not, 20 for Herod feared John, knowing that he was a righteous and holy man, and he kept him safe. When he heard him, he was greatly perplexed, and yet he heard him gladly.