[Someone asked Ibn Umar] about something concerning the pebbles thrown at the Jamarat, and he said, "I do not know whether the Messenger of Allah ﷺ threw them with six or with seven."
أخبرنا محمد بن عبد الأعلى قال حدثنا خالد قال حدثنا شعبة عن قتادة قال سمعت أبا مجلز يقول
عن شيء من أمر الجمار فقال ما أدري رماها رسول الله ﷺ بست أو بسبع
[Its isnad is sahih] Abu Dawud narrated it in the chapter on Rites of Pilgrimage, section, On throwing the pebbles, hadith 1977, from the hadith of Khalid bin Harith, through the same route, and it is also found in al-Kubra, hadith 4084.