Bible: 1 Thessalonians 4 :16

BibleGateway.com - Passage Lookup: 1 Thessalonians 4 :16;

This is a description about death and hope, and the context of it talks about not grieving for those who have died, because all will be brought back at the pretty much same time, in the end. Whenever God Himself declares it, all the world will know and must admit to the Truth, which He is - even those who have died.