You might ask why are so many things in the Bible are twelve in number? The obvious thing is that there are twelve tribes and everything that they do is represented as being done in twelves.
What we miss from this simplified answer is that the ancients counted by the joints of their fingers using their thumbs as pointers, and not their whole fingers as we do. This makes numbers like twelve, sixty, and one hundred forty-four as the significant or marker numbers. Similarly, we view ten, fifty, and one hundred as important markers.
We still have a memory of this early numbering system in one dozen, and we still use their time designation of 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day.
For them, twelve was a hand full and the hand is mans’ greatest servant. So, in the symbolism of the Bible, twelve is the number of those that serve God, or the number of service.
Even though one of their number is no more, Joseph presumably dead, they still say that their service is from the fact that they are twelve.
And they said, “We, your servants, are twelve brothers, the sons of one man in the land of Canaan; and behold, the youngest is this day with our father, and one is no more.” Gen. 42:13
There are twelve tribes.
“Take twelve men from the people, from each tribe a man, Josh. 4:2
The names of the twelve apostles are these: first, Simon, who is called Peter, and Andrew his brother; James the son of Zebedee, and John his brother; 3 Philip and Bartholomew; Thomas and Matthew the tax collector; James the son of Alphaeus, and Thaddaeus; Matt. 10:2-3
There are twelve thrones.
Jesus said to them, “Truly, I say to you, in the new world, when the Son of man shall sit on his glorious throne, you who have followed me will also sit on twelve thrones, judging the twelve tribes of Israel. Matt. 19:28
The New Jerusalem is full of twelves.
It had a great, high wall, with twelve gates, and at the gates twelve angels, and on the gates the names of the twelve tribes of the sons of Israel were inscribed; Rev. 21:12
And the wall of the city had twelve foundations, and on them the twelve names of the twelve apostles of the Lamb. Rev. 21:14
The city lies foursquare, its length the same as its breadth; and he measured the city with his rod, twelve thousand stadia; its length and breadth and height are equal. Rev. 21:16
The foundations of the wall of the city were adorned with every jewel; the first was jasper, the second sapphire, the third agate, the fourth emerald, 20 the fifth onyx, the sixth carnelian, the seventh chrysolite, the eighth beryl, the ninth topaz, the tenth chrysoprase, the eleventh jacinth, the twelfth amethyst. Rev. 21:19-20
And the twelve gates were twelve pearls, each of the gates made of a single pearl, and the street of the city was pure gold, transparent as glass. Rev. 21:21
. . . through the middle of the street of the city; also, on either side of the river, the tree of life with its twelve kinds of fruit, yielding its fruit each month; and the leaves of the tree were for the healing of the nations. Rev. 22:2