What is meant by the first heaven, the one that will pass away? Which one is he talking about?
In the Apostle Paul's second letter to the Corinthians, he says, “Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new" (2 Corinthians 5:17). The first heaven is mostly likely the one in which we now live, the human body, dust of dust, as well as living on the ground of the earth. Therefore, the Christian person may be symbolic of the new creation while this passage may also have a literal meaning. In the Great White Throne Judgment, the Book of Revelations (20:11-15) reveals that the final judgment will end all the former days which the world was subject to sin and death. When all things are made new, death will no longer be a looming threat. The sea which causes a divide will not exist any longer, and all the believers will have no needs other than to be with the Lord. We must also bear in mind that as St. John was inspired to write the details of the Book of Revelation, he could only use human language to describe the indescribable.