a precious stone
The Head of the Corner, The Cornerstone
Isaiah 28:16 (KJV) Therefore thus saith the Lord God, Behold, I lay in Zion for a foundation a stone, a tried stone, a precious corner stone, a sure foundation: he that believeth shall not make haste.
Acts 4:11 This is the stone which was set at nought of you builders, which is become the head of the corner.
12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.