The sin of illegal sexual intercourse
حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، عَنِ الأَعْمَشِ، عَنْ ذَكْوَانَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " لاَ يَزْنِي الزَّانِي حِينَ يَزْنِي وَهْوَ مُؤْمِنٌ، وَلاَ يَسْرِقُ حِينَ يَسْرِقُ وَهْوَ مُؤْمِنٌ، وَلاَ يَشْرَبُ حِينَ يَشْرَبُهَا وَهْوَ مُؤْمِنٌ، وَالتَّوْبَةُ مَعْرُوضَةٌ بَعْدُ ".
Narrated Abu Huraira: The Prophet (ﷺ) said, "The one who commits an illegal sexual intercourse is not a believer at the time of committing illegal sexual intercourse and a thief is not a believer at the time of committing theft and a drinker of alcoholic drink is not a believer at the time of drinking. Yet, (the gate of) repentance is open thereafter."