Riyad as-SalihinChapter 17Hadith 1100
Full Sharh — Riyad as-Salihin 1100
وعن ابن عمر رضي الله عنهما، أن رسول الله صلى الله عليه وسلم قال: "لا يبع بعضكم على بيع بعض، ولا يخطب على خطبة أخيه إلا أن يأذن له" ((متفق عليه، وهذا لفظ مسلم))
English Translation
Ibn 'Umar (May Allah be pleased with them) said:: The Messenger of Allah (ﷺ) said, "A person should not enter into a transaction when his (Muslim) brother has already negotiated, nor should he make a proposal of marriage when that of his brother is pending, except with the permission of the latter."
Source
Riyad as-Salihin(رياض الصالحين)
The Book of the Prohibited actions
Hadith Number
1100