The command is the same as the one in verse 11, and it will be helpful in certain languages to say “write in the book (or, record) the things…” or “you must write in the book the things….” The direct object what you see includes everything John will see and then record in the book. The two clauses that follow are not additional items but define explicitly the nature of what John will see: things present and things future, “both that which is happening now as well as that which will happen afterward” (Bible en français courant; similarly Biblia Dios Habla Hoy, Good News Translation). New Jerusalem Bible shortens and combines the three into two: “Now write down all that you see of present happenings and what is still to come.” The auxiliary verb “will” in “that will happen afterward” (Good News Translation) translates a Greek verb that at times seems to express divine authority. The Arndt and Gingrich Lexicon defines this use of it as follows: “concerning an action that necessarily follows a divine decree, is destined, must, will certainly.”

An alternative translation model for this verse is:

• You must write (or, record) in the book all the things that you are seeing right now, and the things that will happen in the future (or, afterwards).

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .