Ring the doorbell

My friend and I are out together to bring the gospel to people. I get the impression to ring the doorbell of a house; we don't normally do that. A young man, about 20 years old, opens the door, and I tell him the good news. It turns out he's a Christian, recently baptized, and enthusiastic. We're happy, of course! I say, “I have a challenge for you,” and give him the valuable cards to hand out. A week later, we're in the neighborhood again and ring the bell to ask if it worked out. He's happy again and says, "Yes, absolutely, and my brother is joining too, and I've ordered new cards."