A.T. Robertson Commentary John 3:29

"He that hath the bride is the bridegroom: but the friend of the bridegroom, that standeth and heareth him, rejoiceth greatly because of the bridegroom`s voice: this my joy therefore is made full." — John 3:29 (ASV)

The bridegroom (νυμφιος). Predicate nominative without article. Both νυμφη (bride) and νυμφιος are old and common words. Jesus will use this metaphor of himself as the Bridegroom and Paul develops it (2 Corinthians 11:2; Ephesians 5:23–32) and so in Revelation (19:7; 21:2). John is only like the paranymph (παρανυμφιος) or "the friend of the bridegroom." His office is to bring groom and bride together. So he stands expectant (εστηκως, second perfect active participle of ιστημ) and listens (ακουων, present active participle of ακουω) with joy (rejoiceth greatly , χαρα χαιρε, "with joy rejoices") to the music of the bridegroom's voice.

This my joy therefore is fulfilled (αυτη ουν η χαρα πεπληρωτα). Perfect passive indicative of πληροω, stands filled like a cup to the brim with joy.