“Blessed are the pure in heart, for they shall see God.” Matthew 5:8
In Matthew Chapter 5, during the Sermon on the Mount, Jesus delivered eight teachings called The Beatitudes. Beatitudes comes from the Greek word beatus, meaning happy or blessed. Each Beatitude names a virtue and lists an eternal reward for that virtue.
Matthew Henry says the following about this verse:
The pure in heart are happy; for they shall see God. Here holiness and happiness are fully described and put together. The heart must be purified by faith, and kept for God. Create in me such a clean heart, O God. None but the pure are capable of seeing God, nor would heaven be happiness to the impure. As God cannot endure to look upon their iniquity, so they cannot look upon his purity.
Who can be pure in heart? Only those who have given their lives to Jesus. A pure heart has no ulterior motives, no deceit, no duplicity. An absolutely pure heart does not exist in this life. Our hearts become more pure through the process of sanctification once we have been justified by God. We should work daily to control our thoughts and actions. We should pray daily for God to make us aware of those sins that still inhabit our not yet pure hearts.
The purification is completed when we pass from this life into the eternal presence of God. At that time, the pure in heart will see God.