When studying the Bible, it can sometimes be confusing trying to figure out what something means. Sometimes, it seems like words can mean something different in different places in the Bible.
The Rule of First Mention is one way those that study the Bible use to discover the meaning of a word, phrase, verse, or doctrine.
When something is mentioned in Scripture the first time, the same meaning for that verse holds true for subsequent verses.
So, if your reading the Bible and want to clarify what something means, look to see where it is first mentioned in the Bible to discover its meaning