"Blessed are they which do hunger and thirst after righteousness: for they shall be filled." (Matthew 5:6)

"Blessed are ye that hunger now: for ye shall be filled." (Luke 6:21a)

Whether you are actually hungry or you hunger and thirst after righteousness, the feeling is the same — empty. 

The longing to be filled with food is a desire for something outside of you to be given to you to fill up your emptiness.  And so it is when we hunger and thirst after righteousness. 

We are not desiring or claiming any power or goodness of our own. We are empty. There is nothing in us that can help. 

When we see that even our good works are as filthy rags (Isaiah 64:6), we desire to be filled with an external source of righteousness. We desire to have Christ's righteousness counted to us. This is the only way a lowly sinner could ever stand before a Holy God. 

Thankfully, the promise is that we shall be FILLED! We won't get just a little counted to us leaving the rest up to our faithfulness. No, we will stand before God completely justified by the imputed righteousness of Jesus Christ.