There was once a muslim soldier who participated in many military campaigns against the Romans. On one particular campaign when the mujahiddeen had surrounded a roman city his gaze fell upon a woman in a fortress. He was infatuated by her beauty and sent her a message, asking how he could reach her. She replied, “You must accept Christianity and come up to me in the fortress.”
He did as she advised. The muslims were deeply distressed by this. After some time they met him in the fortress and asked him, “What has happened to the Quran you knew? What has happened to your knowledge? What has happened to your fasting? What has happened to your salaah?” He replied: “I have forgotten the entire Quran, except these two verses:
“Often will those who disbelieve wish that they were muslims. Leave them to eat and enjoy, and let them be preoccupied with false hope. Soon they will come to know.” (Sura: Al-Hijr, verse: 2-3)”
(Al Bidaayah wan Nihaayah, vol: 14, pg: 640)