The number 24 is symbolic of two sets of 12.
Twelve is a crucial number in Revelation. Notice how often this number appears in Revelation, particularly when it talks of the holy city. We have on the gates the names of each of the 12 tribes of Israel and on the foundations of the walls the names of the 12 apostles. For both, the number is linked with the people of God.
In the earthly sanctuary, there were 24 courses of priests who took turns in ministering in the sanctuary (see 1 Chronicles 24:4-19). The 24 elders are continually involved in worship and in presenting prayers from the saints to God (see Revelation 5:8), which is a priestly work.
The evidence suggests the 24 elders in Revelation 4 are glorified saints who represent the redeemed of all ages.
We are not told how they got to be in heaven but some have suggested they could be those who were raised when Jesus died (see Matthew 27:51-53). If we put this alongside
what Paul says in Ephesians 4:8, we know when Jesus ascended to heaven He took a host of “captives” with Him. We could then have our answer: they went to heaven with Him as witnesses from humankind to God’s fairness in all His actions.
As the preparations for the inauguration ceremony in heaven got underway, these representatives of humanity would be ushered into the throne room before the ceremony began. In this way, envoys from the whole universe, including humans, are able to express their approval at Christ’s enthronement in Revelation 5.
In verse 5, the “seven spirits of God” is most likely a reference to the Holy Spirit in completeness. The number seven is used in Revelation to denote fullness and perfection.
In verse 6, we see four living creatures: a lion, an ox, a man and a flying eagle. The descriptions of these creatures resemble the creatures Ezekiel saw in his vision and are identified as being cherubim (see Ezekiel 10:20-22).