This is a beautiful story that starts off a little sad, but has a happy ending.
There was boy from Bnei Brak who, unfortunately, left the religion and moved in with an irreligious cousin somewhere else in Israel.
Then things got worse, and he became engaged to a non-Jewish girl. Even his irreligious cousin was quite upset, but was unable to convince him to break up the engagement.
However, he did convince him that since he would be cutting ties with the Jewish people and with his family, he should at least go home, and tell his parents what his plans were-face to face.
He agreed and invited himself home for a Shabbat on "his terms."
He spent Friday night smoking on the porch, and Shabbat day found him again on the porch, with his iPhone. His father approached him Shabbat afternoon, and invited him to join a shiur he was going to, given by Rav Aron Leib Shteinman ztz"l, who was the Gadol HaDor.
Interestingly, the boy agreed to go.
After the shiur, his father brought him over to Rav Shteinman, who could see that the young man was quite distanced from Torah. Rav Shteinman looked at him and asked, "How long have you not kept Shabbat?"
The boy answered "Two years.”
"And during that time, did you ever have a hirhur teshuva/ a feeling of teshuva?"
"Yes,” the boy answered, “About four times."
"And how long did that feeling last each time,” the Rabbi asked.
"Approximately 10 minutes."
"Oh, so it comes out that for 40 minutes during the last 2 years, you were on the level of a Baal Teshuva/repenting person.
And it says in the place where a Baal Teshuva stands, even a purely righteous person can’t stand. I am jealous of you. Shabbat Shalom."
The boy went home, and returned to his cousin’s house, but Rav Shteinman's words left him no peace. How the Gadol had spoken him, respected him, and loved him! He broke off the engagement and returned to Torah and Mitzvot.
His father later asked him what made him go to the class, after he had been smoking and playing with his iPhone the whole Shabbat.
He replied that when he was in 4th grade, his class was tested by Rav Shteinman.
The boys were asked very simple questions. Each boy, upon answering a question received a candy from Rav Aron Leib. When this boy's turn came, he did not know the answer to the question. So Rav Aron Leib asked him an easier question. Again, he did not know the answer. So the Gadol asked him an even easier question, which, again, he did not know.
When the test was over, everyone except this boy had a candy beside him. As the boys were leaving the classroom, Rav Aron Leib motioned for him to come over. He told the boy, "In our religion, we reward for effort, not results. All the other boys put in an effort for one question, so they got one candy. You put in the effort for three questions, so you are getting 3 candies."
And with a smile, he handed him 3 candies. And that is why, when his father invited him to go to that Rav's class, he went; Because of the respect and love that Rav Shteinman had shown him 20 years earlier.
That is powerful.
That is a Gadol BTorah.
That is why they have such an impact.
Have a wonderful day