How do we know that the cause we pray for is just?

Determining whether a cause is just requires aligning our desires with the truth of God's Word. In the sermon, it is emphasized that while David may feel justified in his appeals, true justice can only be affirmed through the lens of Scripture. The believer should assess their cause to ensure it reflects the nature of God and His commandments. Ultimately, only Jesus Christ fully embodies justice, and our prayers for justice must be made through His righteousness, recognizing our own failings and the requirement to present our causes before God in humility.