Matthew 5:8 Blessed are the pure in heart: for they shall see God. (kjv)
In order to see God we must be pure. We must not be mixed with any impurities.
How is this possible when we are full of sin? Well, we need to be washed by God. Only the spotless Lamb of God can take away sin.
Psalm 51:2 Wash me thoroughly from mine iniquity, and cleanse me from my sin.
Psalm 51:7 ...wash me, and I shall be whiter than snow. (kjv)
Psalm 51:10, Create in me a clean heart, O God; (kjv)
If we are washed by God, we will certainly see him as he is. To see his purity we must be made pure lest our sin warps our view of him.