If you want to trace every usage of the term, you need to set aside a few days, list all its various translations, and search for each one. I would expect you to find hundreds of verses.
From the few dozen occurrences I just read, I noticed a trend. When “set apart” implies a change in a person, it is a change that applies to every believer, not just to a select few holier-than-thou ministers. In contrast, “set apart” can apply to specific people when it implies being assigned a task, duty, or mission.
Although Paul recommended singleness in certain circumstances (Paul traveled constantly and was under constant threat of assassination or execution), nowhere does scripture require anyone to set themselves apart for singleness for any office in the church. In fact, Peter and most of the apostles were married, and Paul recommends marriage for anyone, including ministers, who feel weak regarding sexual temptation.
Words translated set apart have a wide variety of possible translations and meanings. The term is sometimes literal, sometimes figurative. It can imply a mere physical act, a declaration, or a foreordination. It is wise to look to the context for meaning and even more wise not to lock yourself into any given meaning.
GOD’S. OWN WORDS
8 I am the LORD: that is my name: and my glory will I not give to another, neither my praise to graven images.
9 Behold, the former things are come to pass, and new things do I declare: before they spring forth I tell you of them.
From the words of God in the two verses above, believers you will see and know that the everlasting God had warned us all that He doesn’t want to share His glory with any other thing, whether mankind or other creatures on earth or in heaven, Our creator God had made this decree even before He created the heaven and the earth. This decree is not something that believers should take lightly or ignore or abolish or refuse to do it. God’s feasts, Sabbath, Commandments and New year are the decrees that makes believers a “set apart “ for the unquestionable, unrivalled and unopposed maker of all things on earth and in heaven. “Set apart” is utmost in God’s hearts and believers must adhere to it without asking questions. God has spoken and who can annulled it.
