Faith becomes contagious like a virus or flu bug, through casual contact. When it comes out of quarantine and connects with other believers or makes contact with unbelieving people regularly and intentionally, it can infect many!
Healthy contagious churches have growing people and they have generous people but the also have genuine people.
What is a genuine person?
In terms of our analogy it would mean someone who has a real case of the disease.
How can you be contagious and infect others unless you are infected yourself?
Perhaps the key word in this verse is "sincere". This word has roots in two Greek words "sine" and "cera" which when translated literally mean "without wax". Here's the story behind it:
In the ancient days unscrupulous potters would use wax to seal up the cracks that were created in their kiln. Rather than throwing out their defective pottery they filled the cracks with wax and painted over them making them look first quality. But of course, the unsuspecting buyer who purchased one soon discovered the flaw and knew he had been deceived.
Not only did this reflect poorly on the crooked potter but also on the honest ones. So, in an attempt to distinguish themselves from dishonest pottery merchants the legit ones began displaying signs declaring - "our pottery is sine cera" - without wax!
To have a contagious faith you must be "sincere" - the real deal - not trying to hide your faults but committing those flaws to God. Genuine believers are not perfect in their performance but perfect in their desires and motives.
Like the early Christians, genuine believers don't just claim to love worship - they worshiped - "Every day they continued to meet together in the temple courts".
How can you claim to be a genuine Christian and then be haphazard with worship?
Like the early Christians, genuine Christians don't just claim to love fellowship - they were involved daily in fellowship - "They broke bread in their homes and ate together with glad and sincere hearts".
How can you claim to be a genuine Christian and be careless in your fellowship with your church?
Like the first Christians, genuine Christians don't just claim to witness - they were involved with witnessing to their faith daily - "praising God and enjoying the favor of all the people. And the Lord added to their number daily those who were being saved."
How can you claim to be a genuine Christian and not be clear or consistent with your witness?
Contagious Christians are genuine in their worship, genuine in their fellowship and genuine in their witness. When that happens God's Spirit is unleashed to call unbelievers to faith!
Genuine faith lowers the level of resistance non-believers so they can "catch" the contagious faith of sincere believers!