The “seven spirits” stand for God’s power and omniscience and
intervention in the events of history. In Zechariah 4:10 divine power
is symbolized by the seven “eyes of the Lord, which range the whole
earth”. Further on in the Apocalypse (5:6), St John tells us that the
seven spirits of God sent out into all the earth are the seven eyes of
the Lamb, that is, Christ. This symbolism (also found in the Old
Testament: cf. Is 11:2ff) is used to show that God the Father acts
through his Spirit and that this Spirit has been communicated to Christ
and by him to mankind. So, when St John wishes grace and peace from the
seven spirits of God it is the same as saying “from the Holy Spirit”,
who is sent to the Church after the death and resurrection of Christ.
Patristic tradition was in fact interpreted the seven spirits as
meaning the septiform Spirit with his seven gifts as described in
Isaiah 11:1-2 in St Jerome’s translation, the Vulgate.