Seven Spirits of God
The Seven Spirits of God are a reference to the Holy Spirit in both the Old Testament and the New Testament. They are typically represented in Scripture as either seven lamps or the seven eyes of God.
In the Old Testament
The Seven Spirits of God are first mentioned in the Book of Zechariah:
1 And the angel that talked with me came again, and waked me, as a man that is wakened out of his sleep. 2 And said unto me, What seest thou? And I said, I have looked, and behold a candlestick all [of] gold, with a bowl upon the top of it, and his seven lamps thereon, and seven pipes to the seven lamps, which [are] upon the top thereof: 3 And two olive trees by it, one upon the right [side] of the bowl, and the other upon the left [side] thereof. 4 So I answered and spake to the angel that talked with me, saying, What [are] these, my lord? 5 Then the angel that talked with me answered and said unto me, Knowest thou not what these be? And I said, No, my lord. 6 Then he answered and spake unto me, saying, This [is] the word of the LORD unto Zerubbabel, saying, Not by might, nor by power, but by my spirit, saith the LORD of hosts. 7 Who [art] thou, O great mountain? before Zerubbabel [thou shalt become] a plain: and he shall bring forth the headstone [thereof with] shoutings, [crying], Grace, grace unto it. 8 Moreover the word of the LORD came unto me, saying, 9 The hands of Zerubbabel have laid the foundation of this house; his hands shall also finish it; and thou shalt know that the LORD of hosts hath sent me unto you. 10 For who hath despised the day of small things? for they shall rejoice, and shall see the plummet in the hand of Zerubbabel [with] those seven; they [are] the eyes of the LORD, which run to and fro through the whole earth. Zechariah 4:1-10 (KJV)
That is, the seven lamps (verse 2) are the Spirit of God (verse 6) and are God's eyes, which "run to and fro through the whole earth" (verse 10).
In the New Testament
The Seven Spirits of God are mentioned more explicitly in the Book of Revelation, in language linking the concept to the above-quoted passage from Zechariah:
And unto the angel of the church in Sardis write; These things saith he that hath the seven Spirits of God, and the seven stars; I know thy works, that thou hast a name that thou livest, and art dead. Revelation 3:1 (KJV)
And out of the throne proceeded lightnings and thunderings and voices: and [there were] seven lamps of fire burning before the throne, which are the seven Spirits of God. Revelation 4:5 (KJV)
And I beheld, and, lo, in the midst of the throne and of the four beasts, and in the midst of the elders, stood a Lamb as it had been slain, having seven horns and seven eyes, which are the seven Spirits of God sent forth into all the earth. Revelation 5:6 (KJV)
The lamps and the eyes are explicitly identified as the Seven Spirits of God, as are the horns. The above passages also show the relation of the Seven Spirits of God to the Lamb, i.e., Jesus Christ.