The above quote, I believe, has been attributed to Bono, the frontman of Irish rock group U2. I take ittomean that he likes to put his faith under scrutiny, to embrace challenges to his faith, to be stretched. This is good practice. Beating our faith up builds resilience, the quality of a flexible durability, a strength, muscle memory we could say. It's like going to the gym - painful and difficult at the time, but of great benefit as it strengthens us. Gradually, the strain of the exercise eases.
The New Testament book of Acts tells the story of what happened to Jesus' first followers when he was no longer physically with them. One of the main characters in this book is Simon Peter, who had been Jesus' right hand man. Like the rest of the Twelve disciples, Peter was Jewish. Even though he had taken the risk on following the unorthodox Jesus, Peter still considered himself a Jew. This still informed Peter's worldview, still influenced his behaviours and attitudes. He largely spent his time among other Jews.
So in chapter 10 of Acts we come to a watershed in Peter's life, and the church's. Peter has been touring Lydda and Joppa. And while he's in Joppa, he stays at the house of another Simon, a tanner. And while he's staying with Simon, during prayer, he has this rather weird vision where he is invited to eat a non-kosher picnic, as a sheet is lowered from heaven with unclean animals in it (animals that Jews were not permitted to eat, not dirty beasts). Peter refuses, The voice says to him, 'don't call unclean what God has made clean'... And, because it's the bible, this happens three times. Then Peter is made aware of some men looking for him, and it turns out they've been sent by a Roman centurion called Cornelius, living in nearby Caesarea (about 30 miles up the coast). Anyway, Cornelius is a good Roman centurion (possibly retired), a God-fearer, well-disposed to Jews. He wants to hear about Jesus, so Peter goes with the men. And when they arrive at Cornelius' place, it makes sense to Peter: he's been discriminating against Gentiles like Cornelius, not mixing with them, not including them in the good news. And suddenly, the church takes its first steps away from Jewish sect toward multicultural, inclusive movement.
But let's go back. Is Peter's realisation so sudden? He's been staying at a tanner's house. What is a tanner? Someone who converts dead animal hide into a flexible and durable material, often used as a tent covering, wineskins, bags and purses, shields, etc. Basically, they made leather. Leather is tough, but malleable. Bikers use it to offer protection.
The tanning process involves steeping, washing, scraping, and more. It was often smelly business, so this was one reason why tanners, whose tanneries were probably their own homes, were marginal people. Simon lived in seaside town Joppa, but specifically he lived by the sea, so possibly out of town. Tanning may also have been religiously dubious occupation, given the contact with dead animals (I believe this issue has been debated).
So maybe Peter, by moving in with a tanner, was already broadening his horizons. Maybe Peter was already re-thinking his worldview. His faith up to this point was never going to take him to Cornelius' house or beyond. But at the tanner's house, his beliefs and attitudes and thinking were converted into something flexible and durable. He learned to beat his faith up. We all need to go to the tanner's house sometimes.