What is the correct size and number of pebbles for stoning the الجمرات?

The pebbles should be slightly larger than a chickpea (approximately 1-2 cm), as described in the hadith: النبي (صلى الله عليه وسلم) picked up pebbles 'like date stones' (small pebbles) for stoning (صحيح مسلم 1299). الشيخ ابن عثيمين stated: 'The pebbles should be between the size of a chickpea and a date stone. Using rocks or large stones is prohibited, and using very tiny pebbles may not fulfill the obligation.' The الحاج needs: 7 pebbles for الجمرات al-Aqaba on the 10th; and 21 pebbles per day for the 11th, 12th (and 13th if staying). Total: 49 pebbles minimum (70 if staying for the 13th). Collecting extra pebbles as backup is مستحب. الشيخ ابن باز stated: 'There is no harm in picking up a few extra pebbles in case some miss the target.' Pebbles may be collected from anywhere — there is no requirement to collect them specifically from مزدلفة.