Abu al-Tufayl (may Allah be pleased with him) said: I asked Sayyiduna Ibn Abbas (may Allah be pleased with them both) about the pebbles with which the Jamrahs have been stoned since Islam came, and he said: "Whatever of them was accepted was taken up, and whatever was not accepted was left; and were it not for that, the space between the two mountains would have been blocked."
In the narration of Sufyan al-Thawri, it is reported from Sayyiduna Ibn Abbas (may Allah be pleased with them both): "An angel has been put in charge of it; whatever of it is accepted is taken up, and whatever is not accepted is left behind."
Ibn Abi Nu'm (may Allah have mercy on him) said: I asked Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) about the pebbles, and he told me: "Those of them that are accepted are taken up; and if it were not so, a mountain higher even than Mount Thabir would have formed here."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9543