What does Psalm 122:8 mean?

This psalm has prayed for the peace and security of Jerusalem (Psalm 122:6–7). Included in this were those who traveled to the city for yearly worship feasts (Deuteronomy 16:16). Naturally, prayers for safety of the city would also imply requests for protection over those who lived there. These are the "brothers" and "companions" of the psalmist, who is likely David. It is honorable for someone to pray for the well-being of others.

In the new covenant church, Christians should love one another and pray for one another. Jesus commanded His disciples to imitate His love by loving fellow believers (John 15:12). His example was that of self-sacrificing and selfless love. He sacrificed His own life for them on the cross. Anything short of that is not Christlike love. It is also a mark of genuine love to pray for one's fellow believers. John 17 presents Jesus' High Priestly Prayer for His followers. When Peter was in prison awaiting execution, the church offered "earnest prayer" for him (Acts 12:5). Philippians 1:9 reports that Paul prayed for the Philippians. In 1 Thessalonians 5:25 he asks the Thessalonian believers to pray for him, and in 2 Thessalonians 1:11 he writes, "we always pray for you."