Genesis 18:21 (KJV) states, "I will go down now, and see whether they have done altogether according to the cry of it, which is come unto me; and if not, I will know." This verse is part of the story of Abraham and Sarah, and it occurs during the visit of three angels to Abraham and Sarah, during which they inform Abraham and Sarah that Sarah will bear a son despite her old age.

This verse encapsulates several important themes found throughout the Bible, including justice, mercy, and the nature of God. The verse demonstrates God's concern for the well-being of His people and His desire to ensure justice is served. It also shows that God is all-knowing and just, and He will not act without thoroughly investigating a situation.

The context of this verse is important for understanding its significance. In the preceding verses, Abraham is conversing with the Lord and pleading for the city of Sodom, asking if the Lord will spare the city if there are righteous people within it. The Lord agrees to spare the city if there are even just ten righteous people. This interaction reflects the mercy and justice of God, as well as the theme of intercession and prayer.

In Genesis 18:21, the Lord informs Abraham of His intention to investigate the situation in Sodom and Gomorrah to determine if the outcry against the cities is justified. The verse reveals God's commitment to justice and His willingness to personally intervene in earthly affairs to ensure righteousness is upheld. This concept of divine intervention is a recurring theme throughout the Bible, illustrating God's active involvement in the lives of His people and His dedication to upholding justice and righteousness.

The symbolism in this verse can also be interpreted in various ways. One interpretation is that God's decision to "go down" to investigate the cities represents His willingness to engage with humanity on a personal level. This mirrors the Christian belief in the incarnation of Jesus Christ, God's ultimate act of approaching and dwelling among humanity to bring salvation and justice.

Another interpretation of the verse is the idea of divine omniscience. When the Lord declares, "if not, I will know," it conveys His all-knowing nature and His ability to discern the truth. This serves as a reminder of God's omniscience and His perfect understanding of all things.

Overall, Genesis 18:21 (KJV) is a pivotal verse in the story of Abraham and Sarah, and it holds profound theological implications. It highlights the themes of justice, mercy, and divine intervention, as well as providing insight into the character of God and His active involvement in human affairs. The verse also offers meaningful symbolism that can be applied to the Christian understanding of God's nature and His relationship with humanity.