Mishkat al-Masabih #2292

Al-Harith b. Muslim at-Tamimi quoted his father as saying that God’s messenger told him secretly to say seven times when he had finished the sunset prayer, before speaking to anyone, “O God, protect me from hell”; for if he said that and died that night, exemption from it would be recorded for him. He also told him to say that when he had prayed the morning prayer, for if he died that day, exemption from it would be recorded for him. Abu Dawud transmitted it.