Sunan An-Nasa'i - سنن النسائي
26. The Book of Marriage - كتاب النكاح
20) Chapter: Prohibition of Proposing Marriage To A Woman When Someone Else Has Already Proposed To Her
Narrated Ibn 'Umar:
It was narrated from Ibn 'Umar that the Prophet said: "None of you should propose marriage to a woman when someone else has already proposed to her."
20) باب النَّهْىِ أَنْ يَخْطُبَ الرَّجُلُ عَلَى خِطْبَةِ أَخِيهِ .
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ . " لاَ يَخْطُبْ أَحَدُكُمْ عَلَى خِطْبَةِ بَعْضٍ "