“The stone that the builders rejected”
Have you never read in the Scriptures: 'The stone the builders rejected has become the cornerstone. This is from the Lord, and it is marvelous in our eyes'? (Matthew 21:42 BSB)
What it sounds like today
A construction metaphor loosely attached to the vineyard story.
The cultural key
Psalm 118 again, the same pilgrim psalm the crowds sang at the entry ('Hosanna… blessed is he who comes'). The rosh pinnah is the cornerstone or capstone on which the whole structure depends: the stone the experts examined and threw on the reject pile turns out to be the one the building cannot stand without. 'Builders' was even a rabbinic term for the learned. And beneath the Hebrew sits a likely pun sealing it to the parable, ben (son) and eben (stone): the rejected son returns as the rejected stone.
Recovered meaning
The experts' verdict is not the final inspection. The son the tenants killed becomes the stone the builders tossed, and God makes that exact reject the load-bearing point of the whole new structure.