John Gill Commentary Revelation 1:3

"Blessed is he that readeth, and they that hear the words of the prophecy, and keep the things that are written therein: for the time is at hand." — Revelation 1:3 (ASV)

Blessed [is] he that reads
This book the Revelation, privately, in his closet or family, carefully and diligently, with a desire of understanding it; or publicly in the church of God, and endeavours to open and explain it to others; and may allude to the reading of the law and the prophets in the synagogues, which were not barely read, but expounded; see (Acts 13:15) (15:21) ; This may be thought to be the sense, especially since there is a change of number in the next clause,

and they that hear the words of this prophecy ;
that listen attentively to the reading and exposition of this book, and have ears to hear, so as to understand the prophecies contained in it: for the whole, when delivered to John, was a prophecy of things to come: but some versions read the number alike in both clauses; as either, "blessed is he that reads, and he that hears," as the Vulgate Latin and Ethiopic versions have it; or "blessed are they that read, and they that hear," as the Arabic version.

and keep those things which are written here ;
the last version adds, "concerning this frail world"; who not only read, and hear, but put in practice what they read and hear; for there are some things in this book which are of a practical nature, especially in the epistles to the seven churches; or the sense is, happy are those persons that observe and take notice of what is written here, meditate upon it, weigh it well in their minds, and retain it in their memories. Now, though eternal happiness does not depend upon, nor is procured by any of these means, as reading, hearing, and observing; yet there is a real happiness, a true pleasure, that does attend these things, which may stir up to a regard unto them; and for which purpose the following words are added:

for the time [is] at hand ;
when these things should begin to be fulfilled.