We can't get away from God. He is the Omni of all omnis, omnipresent (everywhere), omniscient (all-knowing) and omnipotent (all-powerful).
God's presence is a two-edged sword. He travels with us whatever road we venture on. When we find ourselves in the deepest pit (whether our own fault or not), He is there with is. I cling to that faith as I sense I am about to undergo another valley.
The other side is--we can't find someplace private to sin. We can't go into our rooms, lock our doors, shut the blinds, and hope that God won't see us.
The point God makes in this passage is simple: wherever you live, you still must obey Me. My rules don't change when your address does.
God wants me to be light and salt, a witness, a servant, here in this nursing home.
I should be the same person at church, at home, in my bed and in the kitchen, in front of the television set or writing a devotional. Consistency.
Purity is a word the Bible uses to describe it: 100% commitment. No pretense when it comes to our faith. No change or alteration.
Does this mean God demands perfection? Not really. John's letter says that is we say we have no sin, we're lying.
What God does want is a heart after God, like David had. He was a murderer and an adulterer - but he loved God with all his heart.
That's what God wants from us. Not our perfection but our love, our focus.
Holiness grows out of that relationship.