Sayyiduna Uqbah bin Amir (may Allah be pleased with him) narrates from the Messenger of Allah (peace and blessings be upon him) that he (peace and blessings be upon him) said: "None of you should buy over the sale of his brother, nor propose marriage over his proposal."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14945