A companion says: Once we were on a journey with the Prophet (peace be upon him). Since there were few riding animals, people would take turns riding. On one occasion, it was the turn for the Prophet (peace be upon him) and me to dismount. The Prophet (peace be upon him) came close to me from behind and placed his hand on my shoulders and said, "Recite: Qul a'udhu bi rabbil-falaq." I recited these words. In this way, the Prophet (peace be upon him) completed the surah and I recited it along with him. Then, in the same way, he told me to recite: Qul a'udhu bi rabbin-nas, and the entire surah was recited, which I also recited. Then the Prophet (peace be upon him) said, "Whenever you pray, recite these two surahs in your prayer."