How do we know the doctrine of mourning over sin is true?

The doctrine of mourning over sin is rooted in biblical teaching, particularly in the Beatitudes where Jesus articulates the beatitude of mourning in Matthew 5:4. This mourning is linked to being 'poor in spirit,' which is a condition where one recognizes their need for grace. Additionally, the experiences of great biblical figures, such as King David, illustrate this principle. In Psalm 38, David details his struggle against sin, indicating a constant state of mourning where he confesses, 'My sin is ever before me.' Furthermore, the theological understanding that all believers face a war with sin supports the validity of this doctrine. Mourning instigates a longing for the comfort that only God can provide through Christ, emphasizing that true mourning is met with divine consolation.