Sayyiduna Ibn Umar narrated that the Prophet Muhammad (peace be upon him) forbade us from bidding against someone else's bid, and a person should not send a marriage proposal over the proposal of his (religious) brother until the first proposer gives up his intention or permits him to send the proposal, then it is permissible.
Hadith Referenceاللؤلؤ والمرجان / كتاب النكاح / 892
Hadith Gradingمحدثین:«صحیح»
Hadith Takhrij«صحیح، أخرجه البخاري في: 67 كتاب النكاح: 45 باب لا يخطب على خطبة أخيه حتى ينكح أو يدع»