a story I heard from one of my teachers:
Imam Abu Hamid al-Ghazali had a brother who was of ahl Allah, a person of deep spiritual insight and understanding. At the time when Imam al-Ghazali was known for his mastery of Islamic law and excellence as a teacher, his brother would never pray behind him, for reasons he left unsaid. His mother would often chastise him for this (‘What will people think? They’ll think that there’s some problem between you two, or that you find his prayer unacceptable’) until one day he relented. He went to the masjid where Imam al-Ghazali led the prayer, and after the iqamah was called, he joined the ranks of worshippers. He left immediately after the prayer, his perturbed and troubled feelings apparent on his face.
When Imam al-Ghazali returned home, he questioned his brother about the manner in which he left the masjid, and his apparent unease. His brother replied, “In the first raka’h I saw you in a vast garden, reciting words of the Quran. But from the second raka’h until the end, all I saw was blood, blood, blood… you were swimming in a pool of it…”
Imam al-Ghazali’s face colored, and he confessed: “In the first raka’h I was in a state of khushu’ with Allah [focus and connection]; but in the second, I recalled that a woman had approached me earlier in the day, and asked me a question related to haydh [menstruation], and I became distracted thinking about her question.”
It was shortly after this time that Imam al-Ghazali left his high ranking position as a teacher and scholar and went into seclusion, focusing on purifying his soul and worshiping Allah. It was from this time of spiritual focus that he produced Ihya Ulum ad-Deen, one of the greatest and most influential books of Islamic history.