The book of Revelation refers to "seven spirits of God" (Revelation 1:4, 3:1, 4:5, 5:6) which is also written in lower case in most modern English Bible translations, that indicate that the translators understood these "spirits" are not God Himself.

The Greek word "seven" used in these scriptures means, according to the Strong's Concordance:

hepta:             seven
Original Word:     ἑπτά, οἱ, αἱ, τά
Part of Speech:    Indeclinable Numeral (Adjective)
Transliteration:   hepta
Phonetic Spelling: (hep-tah')

The same word ἑπτὰ is used to number both the seven churches and the seven spirits of God in the same scripture, according to the interlinear Greek translation from BibleHub.

However, the translator of the Complete Jewish Bible choose to translate the text rather to "sevenfold Spirit" and also with a capital letter which indicate this translator understood that the "sevenfold Spirit" is God.

These "seven" spirits seems to be also referred to as "seven horns" or "seven eyes" according to John's prophecy:

I saw a Lamb standing, as though it had been slain, with seven horns and with seven eyes, which are the seven spirits of God sent out into all the earth. -- Revelation 5:6

We know the "Lamb" that "had been slain" refers to Christ (also known as the "Messiah" meaning the chosen Saviour).

The prophecy of Zechariah where he saw a stone that also has "seven eyes" and according to Psalm 118:22 and Isaiah 28:16 Christ is the foundation stone.

Behold, I will bring my servant the Branch. For behold, on the stone that I have set before Joshua, on a single stone with seven eyes, I will engrave its inscription, declares the Lord of hosts, and I will remove the iniquity of this land in a single day. In that day, declares the Lord of hosts, every one of you will invite his neighbor to come under his vine and under his fig tree. -- Zechariah 3:8-10 (ESV)

Christ is also referred as:

• the "stone" or "foundation" (Psalm 118:22 and Isaiah 28:16)
• God's "servant"
• the "branch"
• the "vine"

Zechariah wrote of the next vision:

The angel who talked with me came again and woke me, like a man who is awakened out of his sleep.

And he said to me, “What do you see?”
I said, “I see, and behold, a lampstand all of gold, with a bowl on the top of it, and seven lamps on it, with seven lips on each of the lamps that are on the top of it. And there are two olive trees by it, one on the right of the bowl and the other on its left.”
And I said to the angel who talked with me, “What are these, my lord?”
Then the angel who talked with me answered and said to me, “Do you not know what these are?”
I said, “No, my lord.”
Then he said to me, “This is the word of the Lord to Zerubbabel: Not by might, nor by power, but by my Spirit, says the Lord of hosts. Who are you, O great mountain? Before Zerubbabel you shall become a plain. And he shall bring forward the top stone amid shouts of ‘Grace, grace to it!’”

Then the word of the Lord came to me, saying, “The hands of Zerubbabel have laid the foundation of this house; his hands shall also complete it. Then you will know that the Lord of hosts has sent me to you. For whoever has despised the day of small things shall rejoice, and shall see the plumb line in the hand of Zerubbabel.

These seven are the eyes of the Lord, which range through the whole earth.”

-- Zechariah 4:1-10

From this we can conclude that the "seven spirits" are presented as:

• horns (Revelation 5:6)
• eyes (Revelation 5:6, Zechariah 4:10)
• a lampstand (menorah) with seven lamps and on it seven lips (Zechariah 4:2)

All of these symbols indicate that the "seven" are parts of the same body. A horn on its own is dead, an eye on its own is dead, a menorah with only one lamp is broken. So this could possibly all indicate to seven parts of the same Spirit.

However, some argue that Isaiah 11:2 also reveals 7 different spirits of God:

And the Spirit of the LORD [1] shall rest upon him,
the Spirit of wisdom [2] and understanding [3],
the Spirit of counsel [4] and might [5],
the Spirit of knowledge [6] and the fear [7] of the LORD.

But, it clearly states "the Spirit of the LORD shall rest upon him" in singular form, it does not say "the Spirits" of the LORD and there are no proof that these are seven different spirits.

This scripture could rather be understood as characteristics of the Spirit of the LORD:

The Spirit of the LORD shall rest upon Him:,

• the Spirit's wisdom gives understanding,
• the Spirit's counsel gives might,
• the Spirit's knowledge gives fear (respect) to the LORD

This is also how Paul understood it:

The God of our Lord Jesus Christ, the Father of glory, may give you the Spirit of wisdom and of revelation in the knowledge of him, having the eyes of your hearts enlightened. -- Ephesians 1:17-18 (ESV)

Paul states we have access in one Spirit:

For through him [Christ Jesus] we both have access in one Spirit to the Father. -- Ephesians 2:18 (ESV)

and confirm this later in his letter again:

There is one body and one Spirit -- Ephesians 4:4 (ESV)