The Prophet ﷺ instructed them to throw pebbles at the Jamarat the size of small pellets used for flicking.
حدثنا أبو داود حدثنا رباح المكي عن أبي الزبير
أن النبي ﷺ أمرهم أن يرموا الجمار مثل حصى الخذف
No references are available.
Its chain of transmission is sahih. Abu Dawud is Tayalisi, and Rabah is Ibn Marouf al-Makki, who is deemed trustworthy and has narrations for him in Sahih Muslim. This hadith has come up many times within the hadith on Hajj.