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»
The Messenger of Allah (sallallahu alayhi wa sallam) said, “A Mumin is the brother of another Mumin; and thus it is not permissible for a Mumin 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.”.
Riyad as-Salihin 1780, Book 18, The Book of the Prohibited actions, Hadith 270. 1 min read