The Baal Shem Tov once set out on a long trip to Posen (Poland) for the Sabbath. Like all his journeys, this one too was for a spiritual purpose. He lodged there in the home of a Jewish tailor who lived near a university whose professors and students were known for their anti-semitism. Jews avoided the neighborhood, but a few Jews who worked for the gentiles were tolerated. This tailor sewed their clothes and was allowed to live among them.

The Baal Shem Tov arrived at the tailor's home shortly before Shabbat and, when the time came to pray Minha, he asked his host if there was a minyan. The tailor said that he and his workers and a few other Jews from the neighborhood just made a minyan. When they had all gathered at the tailor's house, the Besht stood up and led the prayers so loudly, with such a thunderous voice and with such fervor and d'vekut, that everyone was astonished by the awesome spectacle.

This loud praying was heard by a gentile student who lived in the house next door, who investigated it and became aware of the Baal Shem Tov's presence there. He then complained about it to a senior professor who was a notorious antisemite. This professor was an intelligent and highly educated man who knew Hebrew and Yiddish and was even well-versed in the Talmud. But his knowledge and studies were for the sole purpose of defaming the Jews. When he heard about the Baal Shem Tov's loud praying, he decided to go to the tailor's house to see for himself what was happening.

He went there and found the Baal Shem welcoming the Sabbath and praying with awesome fervor in a tremendously loud voice. The professor stood there watching all through Kabbalat Shabbat and Maariv. Afterward, at the Sabbath table, the Besht made Kiddush over the wine with great d'vekut. Meanwhile, the professor stood there watching intently, all through the meal and the Grace After Meals. He did not speak a word to the Baal Shem Tov; nor did the Baal Shem Tov speak to him or look at him. Following the Grace After Meals, the professor asked the tailor to let him know, the next day, when the Besht was about to pray the morning service.

The professor went home, but the next morning, when the tailor sent someone to him, he returned immediately, and was present for the beginning of the Sabbath morning prayers. He stood there, silently observing, during the whole service. Afterward, when the Besht went to the second Sabbath meal, the professor also stood nearby during the meal and the Grace, without saying a word to the Besht. But he did not take his eyes off of him and gazed at him with total concentration. Everyone there saw this and was amazed by it. After the Grace, the professor again asked the tailor to inform him about the afternoon prayers. He returned then also and was present when the Besht sat down for the third meal. The professor stood nearby, mesmerized by the sight, for the Besht's d'vkeut was truly astounding; his face literally glowed with the light of the Shechinah. During the meal, the Besht spoke fiery words of Torah in such an extraordinary state of d'vekut, that all present were in awe. The professor also listened with intense concentration, because he understood Yiddish and Hebrew perfectly. After the Grace, the Besht prayed the evening service and then recited the Havdala over a cup of wine, all with great d'vekut. The professor stood there watching and listening, fascinated and amazed. He never spoke to the Besht, nor did the Besht speak to him or look at him. After Havdala, the Besht ordered his coach driver to harness the horses. As the Besht was leaving the tailor's house, the professor was still waiting outside, standing by the door; he could not bear to leave. As the Besht passed by him, he turned his head and gazed into the professor's eyes for just a moment, but that moment was like an eternity. The Besht's eyes spoke to the professor with a powerful message that his heart understood. The Besht left for home. The professor also returned home. But a few days later, he left Poland for Germany, where he converted and became a rabbi and a gaon renowned for his righteousness. People used to remark about the holy glow on his face. He was called "Rabbi Abraham the Righteous Convert." This Rabbi Abraham often told the story of how he stood watching the Baal Shem Tov throughout that Sabbath, and he would say, "I know that the Besht's trip was just for my sake, to lift me up from the depths of the Shells and to enliven my soul with the light of life. During his awesome praying, each word that exited from his holy mouth was a flame that entered my heart and burned up one of the impure powers within me, until they were all consumed. Afterward, when the Besht taught Torah at the table during the Sabbath meal, he awakened flames of holiness within me, until immediately after the Sabbath, I fled from Poland to Germany and converted."