The Hozeh of Lublin, who became famous for his spiritual insight, studied in his youth under the Maggid of Mezeritch.
As was common among hasidic rebbes at the time, the Maggid would usually pray alone.
Only when he reached Ein Kelokeinu, at the end of the morning prayer service, would he summon ten of his disciples in order to finish the prayer with a minyan, a prayer quorum.
One day, one person was missing from the minyan, and since the Hozeh was always nearby, he was pulled into the room.
When the Maggid saw the Hozeh, the Maggid said to his disciples, “Why have you brought him? He is a layabout.”
They began to recite Ein Kelokeinu, and because of what he saw on the spiritual plane, the Hozeh immediately fainted.
The Maggid said to his disciples, “See? I told you he was a layabout.
Remove him and bring someone else who does not see, who is able to say Ein Kelokeinu’’
Rabbi Adin Steinsaltz