1 Peter 2:6-8
6 For it stands in scripture:
"See, I am laying in Zion a stone,
a cornerstone (akrogoniaios) chosen and precious;
and whoever believes in him will not be put to shame."
7 To you then who believe, he is precious; but for those who do not believe,
"The stone that the builders rejected
has become the very head of the corner (kephale gonias),"
"A stone that makes them stumble,
and a rock that makes them fall." (NRSV)
There are three stones used to signify Christ in the bible; cornerstone, capstone, and stumbling stone. The cornerstone was a large stone usually laid at the northeast corner of building to begin a foundation. The builder laid it perfectly level and aligned it in such a way that all other construction could be lined and plumbed accordingly. The capstone was a large stone placed at the top of the corner of two meeting walls. Its weight and design, resting atop the juncture, held the walls together. A capstone could also be the keystone at the apex of an arch. The capstone was the final stone laid. It symbolized completeness, prominence, and glory. A stumbling stone was stone that you … well … stumbled over. Stumbling stones were placed to trip large animals and trap them.
The problem is sorting out which stone is which with regard to cornerstones and capstones in biblical references. I have consulted several commentaries and biblical encyclopedias, and there is considerable disagreement. Here is my take on the difference.
It is my theory that following are equivalents in English, Hebrew, and Greek:
Cornerstone = eben pinnah (stone + angle/corner) = akrogoniaios [akron+gonias] (extreme/pinnacle + angle/corner) or litho goniaios (stone corner)
Capstone/Keystone = rosh pinnah (head of the corner) = kephale gonias (head of the corner)
Three Old Testament passages unmistakably refer to a foundation cornerstone. (LXX means Septuagint.)
4 "Where were you when I laid the foundation of the earth?
Tell me, if you have understanding.
5 Who determined its measurements -- surely you know!
Or who stretched the line upon it?
6 On what were its bases sunk,
or who laid its cornerstone (eben pinat, LXX: litho goniaion)
7 when the morning stars sang together
and all the heavenly beings shouted for joy? (NRSV)
16 therefore thus says the Lord GOD,
See, I am laying in Zion a foundation stone,
a tested stone,
a precious cornerstone (eben pinat, LXX: akrogoniaion), a sure foundation:
"One who trusts will not panic."
17 And I will make justice the line,
and righteousness the plummet; (NRSV)
Eben means “stone” and pinnah means “angle” or “pinnacle.” Figuratively pinnah can mean "chieftain." (Judges 20:2; 1 Samuel 14:38). The context of these two passages make it clear they are talking about a foundation. 1 Peter 2:6 is a paraphrase of this passage. (Romans 9:33 seems to be a paraphrase that combines Isaiah 8:14-15, 28:16.)
Then there is this passage where Jeremiah prophecies against Babylon:
No stone (eben) shall be taken from you for a corner (pinnah)
and no stone (eben) for a foundation,
but you shall be a perpetual waste,
says the LORD. (NRSV)
In other words, Babylon will contribute nothing to the foundation of the new order that is coming.
In Zechariah, we see the significance of the capstone or keystone. Zerubbabel lays the foundation for the new temple and this prophecy declares that no obstacle will prevent him from placing the capstone, thus signifying the temple's completion.
6 He said to me, "This is the word of the LORD to Zerubbabel: Not by might, nor by power, but by my spirit, says the LORD of hosts. 7 What are you, O great mountain? Before Zerubbabel you shall become a plain; and he shall bring out the top stone (roshah eben “head stone”) amid shouts of 'Grace, grace to it!'"
8 Moreover the word of the LORD came to me, saying, 9 "The hands of Zerubbabel have laid the foundation of this house; his hands shall also complete it. Then you will know that the LORD of hosts has sent me to you. 10 For whoever has despised the day of small things shall rejoice, and shall see the plummet in the hand of Zerubbabel. (NRSV)
Then in Psalm 118:22-23 we read:
20 This is the gate of the LORD;
the righteous shall enter through it.
21 I thank you that you have answered me
and have become my salvation.
22 The stone (eben) that the builders rejected
has become the chief cornerstone (rosh pinnah, LXX kephale gonias)
23 This is the LORD's doing;
it is marvelous in our eyes. (NRSV)
As we have seen, rosh means “head.” The phrase is “head of the angle/corner.” That it is a stone (eben) head is picked up from “stone” as the subject of the sentence. The "head of the corner" is almost certainly indicating the keystone that holds an arch in place or a large stone spanning atop other stones; the most elevated part of the gate structure, its focal point, and crowning glory.
Now there is no question that Paul explicitly identifies Christ as the foundation of the church:
1 Corinthians 3:10-11
10 According to the grace of God given to me, like a skilled master builder I laid a foundation, and someone else is building on it. Each builder must choose with care how to build on it. 11 For no one can lay any foundation other than the one that has been laid; that foundation is Jesus Christ. (NRSV)
19 So then you are no longer strangers and aliens, but you are citizens with the saints and also members of the household of God, 20 built upon the foundation of the apostles and prophets, with Christ Jesus himself as the cornerstone (akrogoniaios). (NRSV)
At least one commentator on Ephesians suggests that the apostles are the foundation and Jesus is the capstone, signifying a completion from top to bottom. I question that interpretation. I think in this passage Jesus is the foundation cornerstone to which the apostles are added to create a foundation upon which the rest of the structure will be built. I do not think the capstone/keystone image is present here.
Where I think we do see the capstone image entering the New Testament picture is in multiple quotations from Psalm 118:22. We see it referenced here in 1 Peter 2:7 but it also is referred to by Peter in Acts 4:11. It closes out Jesus’ Parable of the Wicked Tenants in all three synoptic gospels. (Matt. 21:42, Mark 12:10-11, Luke 20:17-19) I find no clues to the cornerstone versus capstone/keystone question from these passages except that, like LXX in Psalm 118:22, the Greek for "cornerstone" is kephale gonias, “head of the corner.”
With all that background it seems most likely that 1 Peter 2 is giving three distinct images of Jesus the “living stone.” (v. 4)
Cornerstone (akrogoniaios) – Jesus is original stone laid in the foundation of the new living temple 1 Peter 2 is describing. Everything is built, plumbed, and aligned with him.
Capstone/Keystone (kephale gonias) – Jesus is the stone in the highest most prominent place. He is the completion of the temple. As he is exalted and put in place, like the people in Zechariah 4:7, the people shout out praises.
Stumbling Stone – For those who will not receive his word and obey, Jesus is a stone over which they keep stumbling. He frustrates their plans and is an obstacle to their agenda. This clearly alludes to Isaiah 8:14-15.
As we are about to see in a couple of posts, Jesus is both Lord and head of the church. I think we see those elements reflected in this stone imagery. I noted the pinnah in Hebrew means “angle” or “pinnacle,” but figuratively it can mean chieftain or ruler. Is there a double meaning here? I think possibly so. As the foundational cornerstone, certainly Christ is the rule or measure to which everything else must conform. In at least this sense, he is a “ruler.”
The capstone/keystone holds the structure together in a way somewhat similar to the way the Greeks perceived that the head keeps the body together. But more importantly, like the head, the capstone/keystone was the highest, most prominent, and glorious part of the structure. This is a quality that has everything to do with status and little to being "one who rules."