“Blessed are the poor in spirit, for theirs is the Kingdom of Heaven.”
Matthew 5:3
Have an empty spirit, ready to receive and obey the slightest instruction, and you will be blessed as the kingdom of heaven is yours.
To be poor in spirit is to be helpless and powerless among those who have received abundance of wisdom and provision. It is a recognition of lack in the face of great resources. More than that, it is an acceptance of this spiritual destitution as a foundation for understanding.
In modern terms, we might say an individual is an empty cup, ready to be filled. The cup, in its “poor” state, lacks the liquid with which it desires to be filled. However, recognizing that it is empty, it is willing to receive with joy the liquid wisdom as it is poured out.
A cup that is already full of its own liquid cannot receive any further instruction, since it is already full. This individual has no room for growth or further revelation.
To be poor in spirit is to keep your cup empty so that you can always have plenty of room to receive whatever wisdom and instruction God is willing to pour into you.
The Core of the Bible 