Imam Ahmad bin Hanbal (may Allah have mercy on him) was told about Ibn Ulayyah that he narrates the hadith from Ibn Jurayj: "There is no marriage without a guardian," and that Ibn Jurayj said: I met al-Zuhri and asked him about it, and he said: I do not know it, though he praised Sulayman bin Musa. Thereupon Imam Ahmad bin Hanbal (may Allah have mercy on him) said: Ibn Jurayj had compiled books, but Ibn Ulayyah's report from Ibn Jurayj is not found in those books.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13603