What does Romans 11:9 mean?

Paul is quoting from familiar Jewish Scriptures in the Old Testament. His goal is to support the teaching that God gives or withholds understanding about what is true based entirely on His choice. To some, God gives the ability to believe Him and others he "hardens" (Romans 9:18). This is not a concept Paul takes lightly, and much of chapter 9 was given to exploring how this idea fits with the idea of a just, fair Creator.

Now Paul quotes from David's Psalm 69, a psalm that is often described as being about Christ Himself. In that sense, then, the verses quoted here could point to the enemies of Christ. In that way, Paul suggests Psalm 69:22–23 could apply to those Jewish people who have rejected faith in Christ.

Paul then uses David's words to suggest that these Jewish unbelievers would be trapped and tripped up and punished by their own "table" when they think they are at peace. They would be fooled into complacency, although they are in mortal danger. Paul seems to add the idea of a stumbling block to the quote, connecting it to Isaiah 8:14, which he also quoted in Romans 9:33.