أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يَخْطُبْ أَحَدُكُمْ عَلَى خِطْبَةِ بَعْضٍ ‏"‏ ‏.‏
Translation
Narrated Abu Hurairah

It was narrated from Abu Hurairah that the Prophet said: "None of you should propose marriage to a woman when someone else has already proposed to her."