Warning! SPOILERS for Ghostbusters: Afterlife
Ghostbusters: Afterlife links back to the original Ghostbusters movie in a major way by reusing the Revelations 6:12 Bible quote foretelling of the apocalypse. Ghostbusters: Afterlife centers on the family of Ghostbuster Egon Spengler (the late Harold Ramis) as they move into his dilapidated farmhouse following his untimely demise and discover his old ghostbusting equipment. Egon’s move from New York to the middle of nowhere is directly related to his supernatural investigations, which come at the cost of his friendship with the other Ghostbusters. The locals have nicknamed him the "Dirt Farmer," on account of him owning a farm, yet not raising crops or livestock. In reality, the farmhouse and barn serve as his base of operations and last stand.
Revelations 6:12 was first quoted by Dan Aykroyd's Ray Stantz in 1984's Ghostbusters to Ernie Hudson's Winston Zeddemore. Discussing religion while driving around in the Ecto-1, Winston asks Ray if he remembers "something in the Bible about the last days, when the dead would rise from the grave?" Ray then recites Revelations 6:12 (misquoting it as Revelations 7:12): "And I looked as he opened the sixth seal, and behold there was a great earthquake, and the sun became as black as sackcloth, and the moon became as blood." Winston adds, "And the seas boiled, and the skies fell. Judgment day." Both come to the realization that this could be the reason for the increase in New York's ghosts.
Similar to the original movie, Ghostbusters: Afterlife uses the Revelations 6:12 quote as a warning of the dangers ahead. At Egon’s farm's entrance is a makeshift barricade of rusty metal sheeting and oil drums, on which is crudely written in yellow paint the Revelations 6:12 quote. In the New Testament, The Book of Revelations prophesizes the end days, with Jesus opening seven seals, each representing God's judgment on the world. The first four seals are commonly known as the Four Horsemen of the Apocalypse (the antichrist, war, famine, and death). The fifth seal reveals the martyrs of God. Taken literally, the sixth seal quoted in Ghostbusters and set-up in Ghostbusters: Afterlife releases natural disasters upon the world, as the apocalypse draws closer. 6:12 also predicts the sun being blocked and the moon turning red. In its metaphorical sense, the passage could alternatively represent civil, political, and social chaos. The seventh seal containing the second stage of God's judgments releases even greater destruction upon the earth.
In the world of Ghostbusters, the sixth seal represents "Gozer the Gozerian," the god of destruction, who was thwarted by the Ghostbusters in the 1984 movie, and who makes a return in Ghostbusters: Afterlife. Egon’s warning isn’t the only reference to the Book of Revelation in Ghostbusters: Afterlife though. Ray also has the 6:12 quote tattooed on the inside of his left forearm, visible when answering the phone in his bookshop, Ray's Occult Books. To him, the Ghostbusters defeating Gozer and saving the world was the highlight of his life, validating everything he believed in, so it would make sense to have a tattoo to mark the occasion.
In life, Egon was unsuccessful in reuniting the Ghostbusters, but writing out Revelations 6:12 at the farm could have been his way of warning them of Gozer's return. With his tattoo keeping it fresh in mind at all times, Ray certainly would have understood its true meaning. Beyond the confines of the story though, it also serves as a nice Easter egg for fans of the original Ghostbusters - at least one of many within the divisive Ghostbusters: Afterlife.