Matthew 5:8: μακάριοι οἱ καθαροὶ τῇ καρδίᾳ, ὅτι αὐτοὶ τὸν θεὸν ὄψονται. 

Blessed are the pure in heart, for they shall see God.

Pure in heart. Pure in the inner-person, the sensibilities, emotions, thoughts, appetites, soul.

The word translated “pure,” is katharos, from which we get the English word 
“catharsis.” It means “pure” in the sense of:

• Ablution
• Abreaction
• Expurgation
• Cleansing
• Purgation of negative emotions 
• Purification
• Release
• Unadulterated

The word meant those things in Ancient Greek, but it also sometimes carried connotations of: 

• A cloudless, sunny, clear day
• Clear, pure, pristine water
• A river that is clear and open
• Land that is free of weeds
• A document free of mistakes
• Being free of debt, liability
• Being free from pollution
• Being clean physically or morally
• Figuratively, a branch that has been pruned to bear fruit

“Catharsis” entered the English language as a medical term used to speak of a cleansing of the bowels. More recently, its primary use is in psychology, where we speak of a catharsis as a cleansing or purifying of negative or destructive emotions, such as self-pity or fear, through their release during psychotherapy. A cathartic experience brings renewal, release of guilt, forgiveness, soothing, healing, or the relieving of stress, often through art or music. 

But, I am a debtor, a field overrun by weeds, a foul, polluted river, a contaminated spring, a vine without fruit. None of my concerted, well meaning, efforts can cleanse, expunge, or purify. I am no more able to make my inner-being pure than the man with the withered hand was able to grasp or the demoniac able to free himself of legions. It must all be the work of pure grace, the gracious gift of a loving God operating in and through me in God’s own way and in God’s own time, to create in me a new heart. 

And that is exactly what God has promised to do.