Here is another perspective on being "yeast" hidden in your community, bringing about the kingdom of Heaven.
Where are you to begin? Begin where you are. Make that one corner, room, house, office, as like heaven as you can. Begin? Begin with the paper on the walls, make that beautiful, with the air, keep it fresh; with, the very drains, make them sweet. Abolish whatsoever makes a lie - in conversation, in social intercourse, in correspondence, in domestic life. This done, you have arranged for a heaven, but you have not got it. Heaven lies within: in kindness, in humbleness, in unselfishness, in faith, in love, in service. To get these in, get Christ in. Teach all in the house about Christ - what He did, and what He said, and how He lived. Teach it not as a doctrine, but as a discovery, as your own discovery. Live your own discovery.
Then pass out into the city. Do all to it that you have done at home.
The City Without a Church by Henry Drummond