Putting an offer over the offer of Another

عن ابن عمر رضي الله عنهما عن النبي صلى الله عليه وسلم قال: نهى النبي صلى الله عليه وسلم أن يبيع بعضكم على بيع بعض ولا يخطب الرجل على خطبة أخيه حتى يترك الخاطب قبله أو يأذن له الخاطب (البخاري رقم 5142)

Hazrat ibn Umar (Radhiyallahu Anhuma) reports that Rasulullah (Sallallahu Alaihi Wasallam) said: “One should not put an offer over the offer of his Muslim brother (i.e. in the case where the purchaser and seller are inclined towards concluding the sale), nor should he send a proposal over the proposal of his Muslim brother (when the both parties are inclined towards the nikah), except if he retracts from the proposal himself, or gives him permission to do so.”