The Messenger of Allah ﷺ said, "No man is to outbid his Muslim brother in a sale, nor is he to propose marriage to a woman his brother has already proposed to."
وبهذا الإسناد عن رسول الله ﷺ أنه قال لا يسوم الرجل على سوم أخيه المسلم ولا يخطب على خطبته