Why is Lazarus regarded as Saint Lazarus? Why or how did he get this title?
The Lord never established any special title or office called “saint.” The term “saint” in the Bible simply refers to any believer in Jesus Christ. Simply, put all Christians are saints according to the Bible.
Notice Paul addresses all those who are in Jesus Christ by faith as “saints” in verse 19. Therefore, Lazarus was a “saint” because he believed in Jesus Christ, just as every person who places their faith in Jesus Christ is also a saint. In fact, if you have trusted in Jesus Christ as your Savior, then you too are a saint.
On the other hand, the Catholic religion (which is not Christianity) uses the word “saint” in a very different, unbiblical way to confer special status to certain historical figures which Catholics view to be worthy of such attention. Catholics invented the practice of designating certain people as “saints” to support their false theology that teaches we must merit entrance to heaven through our good works. This is a false Gospel, because the Bible clearly teaches that faith alone brings a person eternal life:
Contrary to the Bible, Catholics teach that we must do good works to merit Heaven, and Catholics invented the idea of supposedly “super Christians” who have done especially good works that merit Heaven. They call these people saints, but this a false teaching as well.
Please read the following article on the Catholic religion vs. true Christianity: Are Roman Catholics Truly Christian?