Abdullah bin Masud went into the depths of the valley and faced the pillars, placing the mountain at his back. Then he threw the pebbles and said, "This is the standing place of the one upon whom Surah al-Baqarah was revealed."
حدثنا روح حدثنا حماد عن حماد عن إبراهيم
أن عبد الله بن مسعود استبطن الوادي واعترض الجمار اعتراضا وجعل الجبل فوق ظهره ثم رمى وقال هذا مقام الذي أنزلت عليه سورة البقرة
Its isnad is sahih. Hammad, the teacher of Rawh, is Hammad bin Salama. And his teacher Hammad is Hammad bin Abu Sulayman. The hadith is a shortened version of the one before it. "That Abdullah bin Masud" appears in H as "that Abdullah bin Yazid," which is an error, corrected from K.