Acts 4:11

“He is the stone which was set at nought of you the builders, which was made the head of the corner.”

Then to support his case Peter indirectly cites Scripture. The citation is from Psalms 118:22. It is either Peter's paraphrase or a quotation from an unknown source, probably the former. He stresses ‘set at nought' rather than ‘rejected'. He has not forgotten the scenes that he witnessed and the ones he had heard about, when Jesus was truly ‘set at nought'. But that stone, rejected by the builders, was to be made the head of the corner, the capstone. It was the final, vital stone that mattered. This Psalm was one from which citations were made by the crowds when pilgrims entered Jerusalem (see Psalms 118:26). They thus indirectly connected it with the Future One Who would come to Jerusalem in triumph. The inference is plain. The rulers, the ‘builders' of Israel, have rejected Him and set Him at nought, because He did not seem to fit, but God has stepped in and will make Him the cornerstone of the new Israel which holds the whole building together.

Some among those who were sat in the Sanhedrin may have grown uncomfortable at these words. They would remember how when they had challenged Jesus a month or so previously He had told the parable of the wicked tenants who had rented the vineyard and then refused to the owner its true fruits, killing first his servants and then his only son (Luke 20:9). Then Jesus had looked on them and had said, ‘The stone which the builders rejected, the same was made the head of the corner' (Luke 20:17). Now here it was again, the charge that they had rejected God's ‘stone', and that somehow their rejection would lead to His exaltation.

(Incidentally we have here an interesting evidence that Luke is not just putting his own words into Peter's mouth. Had he been doing so surely the quotations would have tied up).