“Anyone who gives you a cup of water to drink because you belong to Christ, amen, I say to you, will surely not lose his reward” (Mark 9:41).
Is there anything simpler than sharing a cup of water with another person? The disciples are not called to be valiant soldiers or great administrators. God promises that merely a cup of water given to someone because of Jesus belongs to Jesus.
Basic goodness from Christian motives opens the door of faith to the world.