Biblical References:
The phrase "the stone the builders rejected" is a significant biblical metaphor found in both the Old and New Testaments. It originates from Psalm 118:22, which states, "The stone the builders rejected has become the cornerstone." This imagery is further developed and interpreted in the New Testament, particularly in the teachings of Jesus and the writings of the apostles.

Old Testament Context:
In Psalm 118, the psalmist celebrates God's deliverance and victory, using the metaphor of a rejected stone becoming the cornerstone to illustrate God's ability to exalt what is despised by men. This psalm is part of the Hallel, a series of psalms (113-118) traditionally sung during Jewish festivals, including Passover. The imagery of the cornerstone is significant in ancient construction, as the cornerstone was the principal stone, crucial for the stability and alignment of the entire structure.

New Testament Fulfillment:
The New Testament writers, under the inspiration of the Holy Spirit, apply this metaphor to Jesus Christ, identifying Him as the rejected stone who becomes the cornerstone of God's redemptive plan. This application is seen in several key passages:

1. Matthew 21:42 : Jesus said to them, "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'?" Here, Jesus addresses the religious leaders, highlighting their rejection of Him as the Messiah. Despite their rejection, God establishes Jesus as the cornerstone of His Kingdom.

2. Acts 4:11 : Peter, filled with the Holy Spirit, declares to the Sanhedrin, "This Jesus is 'the stone you builders rejected, which has become the cornerstone.'" Peter emphasizes that salvation is found in no one else, affirming Jesus' central role in God's salvific work.

3. 1 Peter 2:7 : The apostle Peter writes, "To you who believe, then, this stone is precious. But to those who do not believe, 'The stone the builders rejected has become the cornerstone.'" Peter contrasts the belief of the faithful with the disbelief of those who reject Christ, underscoring the honor and significance of Jesus to believers.

Theological Significance:
The metaphor of the rejected stone becoming the cornerstone encapsulates the paradox of the Gospel: what is deemed insignificant or contemptible by human standards is chosen by God for His purposes. Jesus, though rejected by the religious authorities and crucified, is exalted by God as the foundation of the Church and the source of salvation for all who believe.

Christ as the Cornerstone:
In the broader biblical narrative, Jesus as the cornerstone signifies His foundational role in the new covenant community. The Church is built upon Him, and He is the unifying and sustaining force for believers. This cornerstone imagery also points to the fulfillment of Old Testament prophecies concerning the Messiah, affirming Jesus' identity and mission.

Rejection and Exaltation:
The rejection of Jesus by the builders—symbolizing the Jewish leaders and, by extension, all who reject Him—serves as a warning and a call to faith. The exaltation of the rejected stone as the cornerstone is a testament to God's sovereign plan and His ability to bring about His purposes despite human opposition.

Conclusion:
The stone the builders rejected becoming the cornerstone is a profound biblical theme that highlights the reversal of human expectations through divine intervention. It calls believers to recognize Jesus as the essential foundation of their faith and to trust in God's redemptive work through Christ.