Ahmad bin Hafs al-Sa'di said: Imam Ahmad bin Hanbal (may Allah have mercy on him) was asked, while he was present, about the hadith of al-Zuhri concerning marriage without a guardian. Rawh al-Karabisi said: Al-Zuhri had forgotten this. And he cited as evidence a hadith that Ibn Uyaynah heard from Amr bin Dinar; then he (Ibn Uyaynah) met al-Zuhri, who said: I do not know it. He said: So I told Amr bin Dinar, and he said: He himself narrated it to me, about touching the armpit, that it requires ablution.
Al-Shaykh (may Allah have mercy on him) said: This has also been narrated from al-Zuhri through two other chains, although reliance is on the narration of Sulayman bin Musa.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13606