At the beginning of the Second World War, several gedolim were niftar. When they went to tell the Chazon Ish, he cried and was very distressed. But when they told him that HaRav Boruch Ber zt"l passed away, he closed his door and cried for hours. His crying could be heard far away.
Later HaRav Chaim Brim zt"l asked the Chazon Ish why he cried so hard after the petiroh of HaRav Boruch Ber. The Chazon Ish answered: I am sure that the yegi'as haTorah of HaRav Boruch Ber protected Klal Yisroel from destruction. When this yegi'a was lost to the world, I fear for what will be with Klal Yisroel. I cried and davened to Hashem to have mercy on Klal Yisroel.
Once I told over this story in America. Afterwards someone came over to me and said that he had been at the levaya of HaRav Boruch Ber. HaRav Chaim Grodzensky had also been there. After the levaya HaRav Chaim Grodzensky said that he was worried about what will be with Klal Yisroel now that we have lost the yegi'a of HaRav Boruch Ber which had certainly protected Klal Yisroel.
We learn from the Chazon Ish that limitless yegi'a in Torah, like that of HaRav Boruch Ber, can save Klal Yisroel. Once HaRav Boruch Ber was sitting with some talmidim, and someone asked a very strong question on the sugya they were working on. After a few minutes, HaRav Boruch Ber gave a stunning teretz. After another minute he said that it was not a good answer, and that he wanted to think about it more. He went into his room and sat thinking about it for an hour.
After that HaRav Boruch Ber came out of his room and said that he now has an answer. Everybody was eager to hear what he had to say. Amazingly, it was, word for word, the same answer that he had given an hour earlier.
When the talmidim commented on this, HaRav Boruch Ber said, "True it is the same teretz, but before I said it without yegi'a and now it is after yegi'a and it is something else entirely."
Shiurim and chidushim that were said with this kind of yegi'a must also be learned with yegi'a and not casually.
HaKodosh Boruch Hu is sending us a clear message to be chozer beteshuvah quickly to save ourselves and our dear ones and Klal Yisroel. With the merit of our Torah and tefillah may we be zoche to the coming of Moshiach Tzidkeinu.