Once `Abdu’l-Bahá had been very, very sad, and you know, in His days, there were many of the old believers who were watching Him. The moment He became sad, they tried to make Him happy, to tell stories, or to do something to make Him happy. But He was so sad, almost shrunk in Himself, sitting down at a meeting, suddenly He burst out and said, “I don’t know where the people have learned the art of backbiting.” It seemed that He had been very sad about it. Somebody had said something. One of the old believers got up and bowed to the Master, and said, “Beloved Master, from God Himself.” The Master said, “How?” He said, “Adam ate one apple only in his life. God mentioned it in the Old Testament, in the New Testament, in the Qur’án, in all the Tablets.” How beautiful the entire sadness was taken from `Abdu’l-Bahá!

This story was told by Abu’l-Qasim Faizi in one of his talks (from Conqueror of Hearts:
Excerpts from Letters, Talks, and Writings of Hand of the Cause of God Abu’l-Qásim Faizí)