“Holy leaven”, this is a concept or term I have been contemplating lately. What a beautiful thing it is, though we often see leaven in a negative light; i.e the forces of the world creeping into our lives and producing waywardness and death, which it indeed is a picture of, as the Bible describes. But also, we are holy leaven in the world we live in, beloved. Also when we think of missions, we are that holy leaven, transporting the knowledge of the kingdom of our God. In nations, peoples, families, the population surrounding us, wherever that is, we bring the the good news of salvation and the true knowledge of God with us. Go, be the good leaven and feet of the Kingdom of God to your surroundings, in your workplace, families, classes, your one on one interlocutions, exchanges in cafes, or in nations and lands where there is little or no knowledge of God. And, teach others that accept the Word, that they too now are holy leaven.

He told them another parable. "The kingdom of heaven is like leaven that a woman took and hid in three measures of flour, till it was all leavened." - Matthew 13:33 (ESV)

God has placed you in your surroundings, “hidden you”, in the sense of this parable. He placed you in your city, family, immediate daily surroundings, etc. to be the agent of change. And perhaps He is sending you (or calling you to send) to far-away, outwardly-looking difficult surroundings, into frontiers in which you may very well actually feel you need to be somewhat hidden, still to be the agent of His holy change.