(20) باب النَّهْىِ أَنْ يَخْطُبَ الرَّجُلُ عَلَى خِطْبَةِ أَخِيهِ .
It was narrated from Abu Hurairah that the Messenger of Allah said:
"None of you should propose marriage to a woman when someone else has already proposed to her, unless he marries (and he gives up the idea), or gives him permission." (ES)
Reference (ES): Sunan an-Nasa'i 3241 (ES)
In-book reference (ES): Book 26, Hadith 46 (ES)
English translation (ES): Vol. 4, Book 26, Hadith 3243 (ES)