Blessed are the poor in spirit, for theirs is the kingdom of heaven.
— Matthew 5:3

The first beatitude pronounces that God is favorable to the “poor in spirit.” To be poor in spirit means to recognize our spiritual poverty before God. It is to embrace consciously the truth of Romans 3:10-19.

as it is written:

“None is righteous, no, not one;
no one understands;
no one seeks for God.
All have turned aside; together they have become worthless;
no one does good,
not even one.”
“Their throat is an open grave;
they use their tongues to deceive.”
“The venom of asps is under their lips.”
“Their mouth is full of curses and bitterness.”
“Their feet are swift to shed blood;
in their paths are ruin and misery,
and the way of peace they have not known.”
“There is no fear of God before their eyes.”

Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God.

There is nothing we have or can do that will merit favor with God. Nothing at all. To recognize this is to be poor in spirit. Every member of the kingdom of God has this characteristic. We may not all have it to the same level, but no one can be part of the kingdom without it. Genuine members of God’s kingdom realize that they are not part of the kingdom by works. They are not part of the kingdom because they are worthy.
And so we see the Gospel of the kingdom in this first beatitude. To be poor in spirit is the strongest statement of the doctrine of justification by faith alone. If there is nothing we can do, then we cannot be justified by works. This means that we must be justified by someone else’s works. That someone else is Jesus Christ. He has died to pay the penalty for all of our sins. He has lived to give us his perfect righteousness. Jesus is saying that we can be confident that God has given us the righteousness of Christ, because we realize that our works merit nothing. If we realize this then “ours is the kingdom of God.”

Being poor in spirit had further application to the Christian.  

1. It means that we should not be prideful.

2. It means that we should not insist on our way.

3. It means that if someone has offended us, we show humility and quietly bring the issue to the person and not spread it around the congregation. This is Matthew 18.

4. It means that we do not look down our noses at others struggling with sins. Instead we quietly help them.