Now, dear reader, the children of God are sanctified people, sanctified to offer spiritual sacrifices to God through Jesus Christ, and we have no right to do anything but serve God. “What,” you say, “am I not to attend to my business?” Yes, and you are to serve God in your business. “Am I not to look after my family?” Assuredly, you are, and you are to serve God in looking after your family, but still you are to be set apart.
You are not to wear the white robe nor the breastplate (see Exodus 28:4), but still you are to think of yourself as being as much a priest as if the breastplate were on your breast, and the white robe about your loins; for you are “priests unto God and his Father” (Rev. 1:6). He has made you a peculiar generation and a royal priesthood (see 1 Peter 2:9), and He has set you apart for Himself (Ps. 4:3).
The Key to Holiness