Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) saw in a dream that he was writing Surah Sad. When he reached the verse of prostration, he saw that the inkwell, pen, and everything near him had fallen into the state of prostration. Then, when he related this dream to the Noble Prophet (peace and blessings be upon him), the Prophet (peace and blessings be upon him) began to perform prostration in it.