How do we know that the beatitude about mourning is true?

The truth of the beatitude 'Blessed are they that mourn' is rooted in the nature of God’s grace and the transformative work of the gospel. In Matthew 5:4, Jesus emphasizes that those who mourn over their sins are in a blessed position, indicating that God's comfort is promised to such individuals. This beatitude corresponds with the biblical narrative, where God promises comfort in our brokenness and sin. For example, in Isaiah 40:1-2, God assures His people of comfort and the pardoning of their iniquities, reinforcing the assurance that mourning over one's sin is met with divine comfort.

Moreover, the concept of comfort following mourning is exemplified through the apostle Paul’s teachings that identify true mourning as producing repentance leading to salvation (2 Corinthians 7:10). This demonstrates that mourning for our sins, borne out of love for God, aligns with the biblical promise that grace triumphs over sin. Hence, the truth of this beatitude is evidenced through both Scripture and the personal experience of believers as they seek reconciliation with God.