The term “crown” comes from the world of competition, specifically sport, with the winner in those days receiving a wreath or garland; the modern equivalent is a gold medal. A major city as Smyrna would certainly have had its sporting competitions with celebrations to present awards. Here it’s Jesus Christ himself who gives the award: life! This “life” is more than escape from death through persecution (though that’s possible; note the word “until” death). The Lord may well use tribulation to bring a child of his through death to the eternal life on the other side. This “life” knows no more tears or pain or grief (Revelation 21:4), but only the glory and pleasures of being eternally with the Lord of life (Psalm 16:11). He who “came to life” (Revelation 2:8) can certainly give this award to the faithful!
10 Do not fear what you are about to suffer. Behold, the devil is about to throw some of you into prison, that you may be tested, and for ten days you will have tribulation. Be faithful unto death, and I will give you the crown of life.