Our Lord's parables of the Kingdom of Heaven, in Matt. 13, show the same downward tendency in relation to what is committed by God to man in responsibility. All is corrupted and debased.
The first thing we find in these parables is the masterstroke of Satan in introducing mere empty profession and worse among the ranks of the true believers. We find the enemy sowing tares among the wheat; in other words, "the children of the wicked one" are seen alongside "the children of the kingdom" (Matt. 13:38).
This prepared the way for further declension as seen in the parable of the mustard seed. "The least of all seeds" becomes "the greatest among herbs," "a tree," an abortion, a monstrosity, "the birds of the air," symbolizing evil, lodging in the branches thereof (Matt. 13:32).
This sets forth the aim of mere religionists desiring to be great in the earth where their professed Lord was rejected and cast out, the opposite of the kingdom of heaven, where "the meek shall inherit the earth." This pretension to earthly splendor and ecclesiastical and political power is seen in its fullest development in the Romish Church with its popes, cardinals, bishops, abbots, monks, prioresses, nuns, stretching its tentacles over the countries of the world, seeking to be higher than the kings of the earth.
Lastly we have the parable of the woman hiding leaven in three measures of meal till the whole was leavened. This sets forth the gradual introduction of evil doctrine undermining the teaching of the pure Word of God (Matt. 13:33). Leaven in Scripture is always symbolic of evil, and here is no exception to the rule.
The sowing of the tares is bad.
The pretentiousness of the tree springing from "the least of all seeds" is bad.
The introduction of leaven in the three measures of meal symbolizes what is bad.