When John ascends to heaven, he sees four (tessares) living creatures, and in the scene in heaven they are mentioned five times (4:6, 8; 5:6, 8, 14).
Then the Lamb begins to open the seals, and the four living creatures cry out. The sixth seal reveals four angels standing at four corners holding back four winds. Within the seals section, the number four is used by itself (that is, not as part of a larger number) seven times (6:1, 6; 7:1 [3x], 2, 11), three times of the four living creatures and four times to enumerate other things. The arrangement is fairly symmetrical:
A. Four living creatures, 6:1, 6
B. Four angels, 7:1
C. Four corners, 7:1
D. Four winds, 7:1
B’. Four angels, 7:2
A’. Four living creatures, 7:11
From the time John enters heaven to the end of the seals section, the word is used 12 times. One is tempted to point out that 12 is the number of Israel, four the number of the land, so that a 12fold use of the number four hints at something that extends to the corners of the land of Israel.
One is further tempted to point out that 5 is the number of military formation, and of manual power (five fingers grasping a weapon or tool). Five uses of “four living creatures” hints that the living creatures are not only guardians of the four-cornered throne, but are the leaders of the fivefold hosts of God. That prepares for their role in the first four seals: The living creatures summon the horsemen as the Lamb opens the seals.
One is even tempted to point out that the sevenfold use of “four” in the seal section hints at a creation or decreation theme. The four living creatures, with the four corner angels who control the four winds, are agents for bringing sword, famine, death, and beasts into the land (6:8) and for “harming the earth and the sea” (7:2).
In the remainder of Revelation, the word “four” is used another seven times. There are four horns on the altar (9:13), four angels at the Euphrates (9:14-15); the four living creatures put in a few more appearances (14:3; 15:7; 19:4), and finally the nations comes from the four corners of the land for a final battle (20:8). These too are arranged with some symmetry:
A. Four horns, 9:13
B. Four angels, 9:14-15
B’. Living creatures, 14:3; 15:7; 19:4
A’. Corners, 20:8