Jesus begins this parable by comparing the kingdom to a mustard seed. There is some disagreement among commentators concerning the exact type of seed Jesus referred to here.
Mark 4:31 declares that this type of seed is "smaller than all the seeds of the earth." Some believe that Jesus was speaking in a relative sense. That is, He was declaring that the mustard seed, relative to the size of a mature plant, is the smallest of all seeds. However, I see no reason to embrace this interpretation. I believe Jesus' words should be understood literally in context; that is, Jesus was referring to types of seeds that are planted in the earth. Among those seeds, the mustard seed is the smallest. I have read about a plant that has seeds not much bigger than dust particles. This particular plant seems to match the description Jesus supplied. In a mature state, it looks like a small tree with a few leaves and many yellow, trumpet-shaped flowers. Such a plant would easily be capable of providing shade and a nesting place for birds. Regardless of the exact type of seed Jesus was referring to and whether he was speaking in a relative or literal sense, His point is unchanged. The kingdom of God (i.e., the church) will start out exceedingly small and grow to be extraordinarily large. Although the church would start out with a small group of insignificant men, it would grow to enormous proportions. This prophecy has certainly come true!
Jesus continued teaching with parables in Matthew 13:33 - "The kingdom of heaven is like leaven, which a woman took and hid in three measures of meal till it was all leavened."
In Jesus' day, yeast (i.e., leaven) was not preserved in a separate form. A piece of leavened dough that had been set aside from the last baking would be added to the new dough to cause it to rise. It appears that "three measures of meal" was the usual quantity used for one baking. A "woman" is mentioned here because baking was a common part of a woman's household duties. Physically, the yeast (or leaven) quietly works its way through the entire mass of dough. The yeast is the active ingredient in baking. Spiritually, the gospel has a similar effect. It has had a gradual yet undeniable effect upon the world through the church. Jesus' church is the active agent for good in the world!
Matthew commented on Jesus' use of parables in 13:34,35 - "All these things Jesus spoke to the multitude in parables; and without a parable He did not speak to them, that it might be fulfilled which was spoken by the prophet, saying: 'I will open My mouth in parables; I will utter things kept secret from the foundation of the world.'" Jesus, on this occasion anyway, did not teach them anything without using a parable. He fulfilled the prophecy quoted here (from Psalm 78:2) in a notable manner. The Lord was the only distinguished teacher in history to use parables so extensively. Through His parables He communicated truths that had been mysteries or secrets from the beginning of time. How blessed were these people to have the opportunity to learn from the Master Teacher Himself! How fortunate it is that we, living two thousand years later, can study these wonderful parables that were recorded by the inspiration of the Holy Spirit! Praise be to God for His holy word!