Sayyiduna Abu Musa (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "There is no marriage without a guardian." Imam Abu Dawud (may Allah have mercy on him) said in some copies: He is Yunus bin Abi Kathir; this is how it was reported from Abu Dawud (may Allah have mercy on him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13627