Riyad as-SalihinChapter 17Hadith 1101
Full Sharh — Riyad as-Salihin 1101
وعن عقبة بن عامر أن رسول الله صلى الله عليه وسلم قال: "المؤمن أخو المؤمن، فلا يحل لمؤمن أن يبتاع على بيع أخيه ولا يخطب على خطبة أخيه حتى يذر" ((رواه مسلم)).
English Translation
'Uqbah bin 'Amir (May Allah be pleased with him) said:: The Messenger of Allah (ﷺ) said, "A Mu'min is the brother of another Mu'min; and thus it is not permissible for a Mu'min to make an offer while the offer of his brother is pending, nor should he make a proposal of marriage while that of his brother is pending till he withdraws his proposal.".
Source
Riyad as-Salihin(رياض الصالحين)
The Book of the Prohibited actions
Hadith Number
1101