A.T. Robertson Commentary Revelation 19:9

"And he saith unto me, Write, Blessed are they that are bidden to the marriage supper of the Lamb. And he saith unto me, These are true words of God." — Revelation 19:9 (ASV)

Write (Γραψον). First aorist active imperative of γραφω as in 1:11; 14:13. The speaker may be the angel guide of 17:1.

It is another beatitude (μακαριο, Blessed) like that in 14:13 (fourth of the seven in the book).

They which are bidden (ο κεκλημενο). Articular perfect passive participle of καλεω, like Mt 22:3; Luke 14:17. Cf. Revelation 17:14. This beatitude reminds us of that in Lu 14:15. (Cf. Matthew 8:11; 26:29.)

These are true words of God (Hουτο ο λογο αληθινο του θεου εισιν). Undoubtedly, but one should bear in mind that apocalyptic symbolism "has its own methods and laws of interpretation, and by these the student must be guided" (Swete).