Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says: A man asked the Messenger of Allah (peace and blessings be upon him): Who is the pilgrim? He (peace and blessings be upon him) said: "The one dishevelled and covered in dust." Another stood up and asked: Which Hajj is best? He (peace and blessings be upon him) said: "The one with raising of the voice (in the talbiyah) and the shedding of (sacrificial) blood." Another stood up and said: O Messenger of Allah (peace and blessings be upon him), what is the "way" (al-sabil)? He (peace and blessings be upon him) said: "A mount and provision for the journey."
This is what al-Shafi'i meant by his statement that among them is what the people of knowledge refrain from affirming; they refrained from it only because the hadith is known through Ibrahim bin Yazid al-Khuzi, and the scholars of hadith have declared him da'if (weak).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8637