(20) باب النَّهْىِ أَنْ يَخْطُبَ الرَّجُلُ عَلَى خِطْبَةِ أَخِيهِ .
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." (RU)
Reference (RU): Sunan an-Nasa'i 3242 (RU)
In-book reference (RU): Book 26, Hadith 47 (RU)
English translation (RU): Vol. 4, Book 26, Hadith 3244 (RU)