Hmm, great question... well He could have been referring to the stones of the Temple that were soon to fall, He could have been referring to Creation since we know they are eagerly waiting for the sons of God, but I think it's probably most Scriptural to say he was talking about us since Peter called us "living stones" and the Spirit writes on the stone "tablets" of our heart. And we have the OT Scripture that says he turns our hearts of stone, to flesh, so I'll say our stoney heart for $1k Ed? Lol.