(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." (ID)
Reference (ID): Sunan an-Nasa'i 3242 (ID)
In-book reference (ID): Book 26, Hadith 47 (ID)
English translation (ID): Vol. 4, Book 26, Hadith 3244 (ID)