Matthew 13:33 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. (See Luke 13:20-21).
The use of leaven in bread making was a common practice in Palestine, waswell known at the time Jesus related this parable, and is well known today. All Jewish people were well versed on when leaven was to be used and when not to be used. During the Feast of Unleavened Bread, including the Day of Passover, no leavened bread was to be eaten in order to remind them of the haste they made in leaving Egypt in which they took only unleavened bread to sustain them on their journey. At other times, leavened bread was made, eaten, and even required in some offerings made by Jewish priests.
Leaven, as we know it today, is yeast. Technically, it is described as fungi, which germinates and multiplies in the presence of starch or sugar producing fermentation that causes aeration (forms air bubbles), which gives bread a light, airy texture. The leavening process occurs when the yeast is added to raw bread dough. In this method, the raw yeast is dissolved in water before it is added. This same process is also accomplished by adding to the bread mixture a small piece of dough in which the leavening process has already taken place. By saving a lump of "starter" dough from the previous batch of bread, the leavening process can continue without adding yeast. It is generally thought that the latter method was probably used more often in biblical days and the leaven referred to in the parable was a lump of "starter" dough.
Leaven has a contagious effect. When placed in fresh bread dough its effect soon spreads throughout the entire piece of dough. This is the effect that takes place in the kingdom of heaven on earth, the body of Christ. This is the effect the New Covenant doctrine has on the receptive heart of one hearing it when it is proclaimed to them. It spreads throughout their minds, altering and replacing doctrines that are contrary to the will of God. A lump of leavened dough has no effect when placed in with other ingredients to make soup. This mixture is not receptive to leaven. The same is true with when the doctrine of Christ is explained to a person that is not open and receptive to its truths. In this case, Christian leaven fails.
The gospel of Christ is the leavening influence for the world. Preaching and teaching are the instruments that convey Christian leaven. Consider the example that took place on the Day of Pentecost when Peter and the other apostles delivered the message of Christ to those that had assembled from all parts of the world to celebrate this Jewish holiday. Although there were many more present, three thousand individuals had receptive minds to their sermon and were added to the body of Christ. They received the message, the leavening effect took place, and they were changed, taking on the same nature as the lump of leaven (God's Holy Word),which was given tothem through the apostles teaching. The lump of "spiritually leavened dough," when placed in a receptive heart, produced a loaf of "spiritually leavened bread" - a Christian.
This Christian leavening process has taken place from the day the church was established on the Day of Pentecost to the present day. The leavening "starter", the lump of leavened dough has been handed down from generation to generation in order to spread the gospel message of God to the receptive hearts of all ages. The leavening "starter" used on the Day of Pentecost is the same "starter" used today. It produced a Christian when taught by the apostles, and it produces a Christian when taught today by faithful gospel preachers and teachers.
As a Christian, how do you affect the lives of those around you? You don't have to be a preacher or classroom teacher to be a Christian leavening agent to others. The world around you is full of receptive hearts searching for the spiritual guidance that will lead them to salvation in heaven. Your Christian influence is the spiritual leaven they need to become to Christ, hear and believe His word, and be baptized into His body, the church. The words you speak, the Christian example you set in your daily life can, and will, have this leavening effect on your family, your friends and neighbors, and all you chance to meet. You hold the leaven. Hide it today; not from others, but in others - in receptive hearts. The result will be a Christian - bread suitable for that great feast in heaven, when we gather around the table of God.