I saw Abdullah go down into the valley, position the pillar to the right of his eyebrow, and face the Kabah. He then threw seven pebbles at it, saying takbir after each pebble, and said, "By the One besides whom there is no god, this is the standing-place of the one upon whom Surah al-Baqarah was revealed."
حدثنا يحيى عن المسعودي حدثني جامع بن شداد قال سمعت
رأيت عبد الله استبطن الوادي فجعل الجمرة عن حاجبه الأيمن واستقبل البيت ثم رماها بسبع حصيات يكبر دبر كل حصاة ثم قال هذا والذي لا إله غيره مقام الذي أنزلت عليه سورة البقرة
Its isnad is sahih. Yahya bin Saeed heard from Masudi early on, then met him after he had become confused in his memory and refused to hear anything further from him. See Tahdhib 6:211. The hadith is abridged from 4061.