Why is the woman who hid leaven in the parable presented negatively?
The woman is presented negatively because leaven in Scriptural analogy always refers to evil, and sin is leaven. She took the leaven and hid it in three measures of meal until the whole lump was leavened, depicting a woman inserting evil into a situation, which displeased God.
Les teaches that leaven in Scripture is always used as a picture of something evil, and sin is leaven. In Matthew 13:33, the kingdom of heaven is likened to leaven that a woman took and hid in three measures of meal until the whole lump was leavened. He explains this is used in a bad light because it was a woman who was guilty of inserting evil into a situation. Earlier, Les connects the same negative idea to the church of Thyatira, where Jezebel called herself a prophetess and seduced servants into immorality and idolatry. He asks whether women would want to be in that position, and the implied answer is no. Thus the woman in the parable is presented negatively because she pictures someone introducing evil that spreads through the whole lump, and God was displeased with it.
Another parable spake he unto them; The kingdom of heaven is like unto leaven, which a woman took, and hid in three measures of meal, till the whole was leavened.