Matthew 5:3-4

"Blessed are the poor in spirit, for theirs is the kingdom of heaven. Blessed are those who mourn, for they will be comforted."

for theirs is the kingdom of heaven
Matthew 5:10 "Blessed are those who are persecuted because of righteousness, for theirs is the kingdom of heaven."
Matthew 5:19 "Anyone who breaks one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven."
Matthew 25:34 "Then the King will say to those on his right, 'Come, you who are blessed by my Father; take your inheritance, the kingdom prepared for you since the creation of the world.'"

for they will be comforted
Isaiah 61:2-3 ... to proclaim the year of the LORD's favor and the day of vengeance of our God, to comfort all who mourn, and provide for those who grieve in Zion--to bestow on them a crown of beauty instead of ashes, the oil of gladness instead of mourning, and a garment of praise instead of a spirit of despair. They will be called oaks of righteousness, a planting of the LORD for the display of his splendor.
Revelation 7:17 "For the Lamb at the center of the throne will be their shepherd; he will lead them to springs of living water. And God will wipe away every tear from their eyes."

Scriptures taken from the Holy Bible, New International Version® NIV®, Copyright© 1973, 1978, 1984 by International Bible Society. Used by permission. All rights reserved worldwide.