What do you picture when you think of the word holy—maybe wearing white robes or a halo, or floating off the ground? That's not holiness; that's just goofiness. Holiness simply means to be set apart for a particular use.
For example, at home I have a coffee-making vessel called a French press. My French press is holy, meaning that I don't put tea bags or hot chocolate in it—only coffee beans ground in a certain way. It is set apart for a particular purpose.
This is the idea behind the ordination ceremony of the ancient priesthood we read about in Leviticus 8: "[Moses] took some of [the ram's] blood and put it on the tip of Aaron's right ear, on the thumb of his right hand, and on the big toe of his right foot" (v. 23), then he did the same to Aaron's sons. Performing this ceremony was like saying, "May this priest hear the voice of God, do the works of God, and walk in the ways of God."
But what does all that have to do with us as believers? In Romans 12, Paul used similar language when he wrote, "I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service" (v. 1).
In other words, he was saying, "You, like the priest, come and voluntarily offer your body for God to work through." That's when life really gets good—when you present your body as set apart for the Lord, as a base of operations through which the Holy Spirit can work to reach other people.
It's interesting to me that God chooses to use and work through His redeemed people. He saves us and then says, "I'll work My ways through you, just as you are, if you let Me." God didn't have to do that. God could have used angels to get the word out instead of redeemed humans—and they probably would've done a much better job than we've done over the last 2,000 years, right? But God has chosen to restrict Himself to do the most important part of His work now through our bodies.
Maybe you're thinking, Not a good plan, God. I would counsel against that. But the reason God does that is because it gives Him more glory. The more imperfect the instrument, the greater the glory goes to the one using that instrument. God used priests in the Old Testament, and He now uses our bodies for His glory.
So here's my question for you: Are you like my French press? Are you set apart not for coffee beans but for the Lord's purposes? Have you dedicated your life to Him? And are you listening to His voice, serving Him, and walking with Him in holiness today?