Matthew 5:4

"Those who mourn" do so because they sense their spiritual bankruptcy (Matthew 5:4). The Old Testament revealed that spiritual poverty results from sin. True repentance produces contrite tears more than jubilant rejoicing because the kingdom is near. The godly remnant in Jesus’ day that responded to the call of John and of Jesus wept because of Israel’s national humiliation as well as because of personal sin (cf. Ezra 10:6; Psalms 51:4; Psalms 119:136; Ezekiel 9:4; Daniel 9:19-20). It is this mourning over sin that resulted in personal and national humiliation that Jesus referred to here.

The promised blessing in this beatitude is future comfort for those who now mourn. The prophets connected Messiah’s appearing with the comfort of His people (Isaiah 40:1; Isaiah 66:1-3; Isaiah 66:13). All sorrow over personal and national humiliation because of sin will end when the King sets up His kingdom and the repentant enter into it.