D&C 128

 The Prophet Joseph Smith taught - 

"...I want you to remember that John the Revelator was contemplating this very subject in relation to the dead, when he declared, as you will find recorded in Revelation 20:12—And I saw the dead, small and great, stand before God; and the books were opened; and another book was opened, which is the book of life; and the dead were judged out of those things which were written in the books, according to their works.

7 You will discover in this quotation that the books were opened; and another book was opened, which was the book of life; but the dead were judged out of those things which were written in the books, according to their works; consequently, the books spoken of must be the books which contained the record of their works, and refer to the records which are kept on the earth. And the book which was the book of life is the record which is kept in heaven; the principle agreeing precisely with the doctrine which is commanded you in the revelation contained in the letter which I wrote to you previous to my leaving my place—that in all your recordings it may be recorded in heaven."  (Doctrine and Covenants 128:6–7)