Mat 5:3 Blessed are the poor in spirit, for theirs is the kingdom of heaven.
Jesus begins the beatitudes by calling those poor in the spirit blessed. They are not recipients but pocessors of blessings. This beatitude sums up the whole sermon because it sets the tone for the rest.
The poor stands in contrast to self sufficient. The foundation of all other graces is laid in humility. The poor have become poor by declaring bankrupt from the things they once counted as assets to save and keep them to Who can save them. Paul writes, Php 3:7-9, “7 But whatever gain I had, I counted as loss for the sake of Christ. 8 … For his sake I have suffered the loss of all things and count them as rubbish, in order that I may gain Christ 9 and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith”
Those who would build high must begin low; the weary and heavy laden shall find rest in Christ in their state of poverty, for the kingdom of God is theirs, Job 5:11 “He sets on high those who are lowly, And those who mourn are lifted to safety”. That is to say they receive that which they have not earned.