Matthew 13:31-46
In the Sower, birds correspond to the evil one. Every other metaphorical use of leaven in the NT is negative. And in every redemptive use of 'purchase,' Christ is the buyer. When you apply the keys Jesus gave in the explained parables to the ones He left unexplained, the standard readings don't survive.
Matthew 13:1-50
Jesus defined His own symbols. In Matthew 13, He gives explicit definitions across three parables — twelve unique equations — and those definitions, not the reader's intuition, govern how every parable should be read.