Musannaf Ibn Abi Shayba 33:1182

Ja'far ibn 'Awn narrated to us, from Sufyan, from Isma'il, from al-Sha'bi: Regarding His saying, "Upon them they ascend" (43:33), he said: The staircases. And regarding His saying, "And roofs" (43:33), he said: The rafters. And regarding His saying, "And gold" (43:35), he said: Gold.