Psalm 136:10 in the King James Version (KJV) of the Bible reads, "To him that smote Egypt in their firstborn: for his mercy endureth for ever." This verse is part of a larger psalm that is focused on giving thanks to God for His enduring love and mercy. In this verse, the psalmist reflects on the event of God smiting Egypt in their firstborn, which references the tenth plague that befell Egypt before the Israelites were freed from slavery.

The context of this verse can be found in the story of the Exodus, which is recounted in the book of Exodus in the Bible. In Exodus 12, God sends the tenth plague upon Egypt, which is the death of the firstborn. This plague leads to Pharaoh finally allowing the Israelites to leave Egypt, marking their deliverance from slavery. The psalmist is acknowledging this significant event in the history of Israel and attributing it to God's mercy.

The theme of God's mercy and deliverance is central to this verse. The psalmist is emphasizing that it was God's mercy that ultimately led to the Israelites' freedom. Despite the hardships and oppression they faced in Egypt, God's mercy endured, and He intervened on their behalf to bring about their deliverance. This theme of mercy is a recurring motif throughout the entire psalm, as the psalmist repeatedly declares, "for his mercy endureth for ever," after each proclamation of God's mighty acts.

The symbolism in this verse lies in the contrast between the judgment upon Egypt and the mercy extended to the Israelites. The smiting of Egypt's firstborn represents the severity of God's judgment upon those who oppress His people. However, it also symbolizes the justice and righteousness of God in fulfilling His promises to deliver the Israelites from their bondage. On the other hand, the enduring mercy of God is symbolized by the fact that, despite the severity of the judgment, He still showed compassion and provided a way for the Israelites to be set free.

In the broader context of the entire psalm, Psalm 136 serves as a litany of praise for God's enduring love and mercy throughout the history of Israel. The psalmist recounts the creation of the world, the deliverance from Egypt, and the conquest of the Promised Land, all as acts of God's steadfast love. The repetition of the phrase "for his mercy endureth for ever" after each declaration emphasizes the unchanging and everlasting nature of God's mercy.

Overall, Psalm 136:10 in the KJV of the Bible reflects the themes of God's mercy, deliverance, and justice. It serves as a reminder of God's faithfulness to His people and His willingness to intervene on their behalf, even in the face of oppression and hardship. The symbolism of the smiting of Egypt and the enduring mercy of God highlights the tension between judgment and compassion, and ultimately points to the redemptive nature of God's love for His people. This verse continues to resonate with believers as a source of hope and assurance in the unchanging nature of God's mercy.