Corrie ten Boom in The Hiding Place relates an incident that taught her always to be thankful. She and her sister, Betsy, had just been transferred to the worst German prison camp they had seen yet, Ravensbruck. On entering the barracks, they found them extremely overcrowded and flea-infested.

That morning, their Scripture reading in 1 Thessalonians had reminded them to rejoice always, pray constantly, and give thanks in all circumstances. Betsy told Corrie to stop and thank the Lord for every detail of their new living quarters. Corrie at first flatly refused to give thanks for the fleas, but Betsy persisted, and Corrie finally succumbed to her pleadings. During the months spent at that camp, they were surprised to find how openly they could hold Bible study and prayer meetings without guard interference. It was not until several months later that they learned the reason the guards would not enter the barracks was because of the fleas.