In the “beatitude” portion of His “sermon on the mount,” Jesus taught, “Blessed are those who mourn, for they shall be comforted” (Matt. 5:4).
There are a few possibilities for what type of mourning would lead one to be blessed by God. Jesus may have been referring here to one who mourns due to persecution, or one who sorrows for the wickedness of the world.
In the immediate context, though, it appears quite possible that Jesus is including one who mourns with godly sorrow over his or her sins.
Notice 2 Corinthians 7:9-10: I now rejoice, not that you were grieved, but that you were grieved to repentance. For you were grieved in a godly way, that you might suffer loss by us in nothing. For godly sorrow produces repentance to salvation, which brings no regret. But the sorrow of the world produces death. One who is poor in spirit (Matt. 5:3) will recognize how grievous sin is, and thus will be led to mourn over his or her sins, and meekly turn to the One through whom we can be forgiven (Matt. 5:5). Those who have such godly sorrow find comfort in the Lord.
– Michael Hickox