Blessed are the pure in heart...
In his book, The Sermon on the Mount, Kent Hughes quotes a nineteenth-century Russian novelist, Ivan Turgenev:
“I do not know what the heart of a bad man is like. But I do know what the heart of a good man is like. And it is terrible.”
Although it is impossible for us to have a pure heart in and of ourselves, we can have a pure heart by the grace of God. What is impossible for man is possible for God. A pure heart is a gift from God, and it comes by a new birth, by a new creation, and by the Spirit living in us.
God had promised in the Old Testament through the prophet Jeremiah, “I will put my law in their minds and write it on their hearts” (Jeremiah 31:33), and “I will give them singleness of heart and action” (Jeremiah 32:39). This was finally fulfilled in and through Jesus Christ, Who makes us a new creation with a new heart (2 Corinthians 5:17).
There are ways we can maintain the purity of our heart, and one of the most primary is our time in the Word of God. As the psalmist said, “How can a young man keep his way pure? By living according to your word” (Psalm 119:9), and, “I have hidden your word in my heart that I might not sin against you” (Psalm 119:11).
A second way to maintain the purity of our heart is through fellowship with the people of God. It helps to be accountable to one another. Solomon said:
Two are better than one,
because they have a good return for their work:
If one falls down,
his friend can help him up.
But pity the man who falls
and has no one to help him up! (Ecclesiastes 4:9-10).
That is why the author of the Book of Hebrews exhorts us, “Let us consider how we can spur one another on toward love and good deeds” (Hebrews 10:24).
Thirdly, we can train our heart for pure living by doing the works of God. As we are involved in His service and as God uses us for the blessing of others, we are encouraged towards our devotion to God and to keeping our hearts morally pure.
Full article here