Jesus says the Kingdom of heaven is like a mustard seed sown in a field, or like some yeast worked into three measures of dough. These passages are usually taken to describe how the Church, or the Christian faith, despite small beginnings, has spread and transformed the entire world for the better. This is a valid interpretation, but the Kingdom of heaven is not only an external reality; it is internally and personally experienced. Since the Scriptures are written not only by human authors, but by the Holy Spirit as well, every passage contains more than one true interpretation. Jesus’ similies also describe faith in the life of individual Christians.
At the beginning of one’s discipleship, the seed of faith is small and vulnerable. Any challenge or trial, any passing bird, can potentially come along and consume it. This seed of faith must be guarded, watered, and given light. This means vigilence, education, and contact with Christ in prayer and the sacraments. In time, faith grows to the point that trials and challenges are no longer a grave threat, but calmly accepted.
The faith of the Christian is also like yeast which is not meant to be merely kept in a jar in on the shelf, segregated to Church or private life. It is meant to be mixed into the whole of life; at home, at work, and everywhere, so that the entire batch of life will be transformed and raised.
If your faith is young and fledging, or a confined and isolated part of your life, be encouraged by the hope these passages promise. The Kingdom of God is at hand for you.