Numan bin Saad reported,
We were sitting with Ali 
when he recited this verse, "The day We will gather the righteous to the Most Merciful as a delegation" [Maryam 19:85].He said, "No, by Allah, they will not be gathered on their feet, and a delegation is never brought on foot. Rather, they will come on she-camels the like of which creation has never seen, mounted with saddles of gold. They will ride upon them until they knock at the gates of Paradise."
Ahmad 1333
Daifحدثنا عبد الله حدثني سويد بن سعيد أخبرنا علي بن مسهر عن عبد الرحمن بن إسحاق حدثنا
النعمان بن سعد قال
كنا جلوسا عند علي رضي الله عنه فقرأ هذه الآية {يوم نحشر المتقين إلى الرحمن وفدا} قال لا والله ما على أرجلهم يحشرون ولا يحشر الوفد على أرجلهم ولكن على نوق لم تر الخلائق مثلها عليها رحائل من ذهب فيركبون عليها حتى يضربوا أبواب الجنة
No references are available.
Its isnad is daif, due to the weakness of Abdul-Rahman bin Ishaq. The hadith appears in Majma al-Zawaid 7:55, where it is faulted on account of Abdul-Rahman bin Ishaq, but a mistake was made in attributing it to Imam Ahmad, for it is actually one of the additions of his son. Ibn Kathir mentioned it in his tafsir 5:401 from this same place, and also attributed it to Ibn Jareer and Ibn Abu Hatim. Suyuti, in Durr Manthur 4:285, also attributed it to Ibn Abu Shayba, Ibn Munzir, Ibn Mardawayh, and Hakim, who graded it sahih, and to Bayhaqi in Bath.It appears in Mustadrak 2:377, where Hakim said, "Sahih according to the criterion of Muslim, though the two of them did not record it." Dhahabi challenged this, saying, "Rather, this Abdul-Rahman was not narrated from by Muslim, nor from his maternal uncle Numan, and the scholars have judged him daif." This hadith and the one before it are both among the additions of Abdullah bin Ahmad.