The Effects of Shatnez

When the Mirrer Yeshiva was temporarily sheltered in Shanghai during World War II, the entire yeshiva felt a powerful stirring to learn Torah and Mussar and pray with special intensity. Although they had been fortunate enough to escape the Germans, they knew that living under the Japanese was no guarantee of safety since the Japanese were allied with Nazi Germany and could turn against the Jews any day. Furthermore, there was no protection against the Allied air raids of Shanghai. The only protection was clearly to be secured from their Father in heaven, through heartfelt prayer, introspection, and diligent learning.
On Yom Kippur, the intensity of the tefillos was hard to imagine. Oddly enough, in the middle of the davening, a certain very prominent student left the beis medrash for a short time and then returned in his weekday outfit. He resumed his tefillah and remained in his place until the end of the long day.
After Yom Kippur, another bochur asked the one who had left why he had done such a strange thing.
The first bochur explained, “When I was davening, I felt that my tefillos were just not flowing with even the kind of intensity that I have gotten used to during an ordinary weekday. I couldn’t understand what I was doing wrong, and so I tried to learn a little mussar. Although this usually is very helpful, this time it did nothing for me. I suddenly realized that my new Shabbos suit might be the culprit. I saw in the Tzionei on Chumash that wearing shatnez prevents ones prayers from ascending. I quickly went to change into my weekday clothes, and as soon as I returned I could tell that my suspicions were right because all the barriers just melted away.”
“But didn’t you check your new clothes for shatnez?” the other bochur asked.
“I did, but my feeling on Yom Kippur made me certain that the one who had checked had missed something.”
The following day, the suit was thoroughly re-examined, and sure enough there were parts that had been processed with linen in a way that was very difficult to detect. The suit was simply riddled with shatnez!