# Beloved

"You whom I love" or "Dear friends"

# let us cleanse ourselves of all defilement of flesh and spirit

Here Paul is saying to stay away from any form of sin that would affect one's relationship with God. 

# of all defilement of flesh and spirit

"of all things in our body and spirit that make us unacceptable to God"

# Let us perfect holiness

"Let us do all we can to be perfectly holy"

# in the fear of God

"out of deep respect for God" or "because we fear God"