Sayyiduna Uqbah bin Amir (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "When two guardians conclude a marriage, the first has the greater right."
(b) In al-Imla' these words are additional: "When two (agents) sell, the word of the first is more valid."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13801