It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that a beautiful woman used to pray behind the Prophet (peace and blessings be upon him). Because of her, some people would look for a place in the front rows so that they would not see her, while others would look for a place in the back rows so that they could get a spot in the last row, and when they bowed (in ruku‘), they would look at her from under their armpits. Upon this, the following verse was revealed: «﴿وَلَقَدْ عَلِمْنَا الْمُسْتَقْدِمِينَ مِنْكُمْ وَلَقَدْ عَلِمْنَا الْمُسْتَأْخِرِينَ﴾ [الحجر: 24] » "We surely know those of you who go forward and We surely know those who lag behind."