I read somewhere that on average, 1 in every 5 Scripture verses contain a number. You don't have to read too much before you notice the frequency of certain numbers.
Just a word of caution before we begin. There is some "off" stuff out there on numbers in the Bible. There are people who read too much into it. Recently there was a guy who predicted the world would end on a certain date last September based on his "study" of frequently used numbers in the Bible. This is hogwash and it irritated me the press gave this goofball so much air time. There are lots of internet sites talking about numerology in the Bible. Just a browsing of them makes me feel very uneasy. They give off the vibe of occult practices. I think we need to be careful about reading too much into the numbers in Scripture.
It is, however, interesting that some numbers are repeated frequently.
I don't begin to profess to know why.
Everything I looked at said the numbers 3, 7, 10, 12 and 40 were the most frequent.
The number 3
Jonah was inside the big fish for 3 days. (Jonah 1:17)
Matthew 26:34 tells us that Peter denied Jesus 3 times.
Jesus rose after 3 days. (Luke 9:22)
Paul was blind for 3 days. (Acts 9:9)
Noah had 3 sons. Job had 3 friends who tried to "comfort" him. Daniel had 3 friends with him. (Genesis 7:13; Job 2:11; Daniel 1:6)
Noah's ark had 3 stories. (Genesis 6:16)
The number 7
The number 7 is the number of completeness and perfection.
Joseph predicted 7 years of abundance followed by 7 years of famine. (Genesis 41:27)
Exodus 12:15 tells us Passover lasted for 7 days.
The Israelites marched around Jericho 7 times on the 7th day with 7 priests blowing 7 trumpets. (Joshua 6:3-4)
Jesus drove 7 demons from Mary Magdalene. (Mark 16:9)
The number 10
The 10 plagues on Egypt, the 10 commandments and the mentioning of 1/10th in a lot of places (tithing) came to my mind when thinking of the significance of the number 10. One of the sources I looked at mentioned there are 10 names in the Bible with 2 letters. Doesn't that seem like they are reaching to find a link between the number 10 and the Bible? I found many examples of obscure facts about numbers in the Bible and it really kind of creeped me out.
The number 12
There were 12 tribes of Israel named after the 12 sons of Jacob.
Ishmael had 12 sons becoming the tribes of the Arab people.
Jesus called 12 men to be his disciples.
The number 40
The number 40 frequently symbolizes a period of testing, trial, probation, or preparation. Whenever I am reading the Bible and I see wandering in the desert for 40 years or 40 years of preparation, I think 'that is just such a long time!' We don't like the times God is preparing us or we find ourselves in a spiritual desert. We want those times over. We want in and out. But typically it was 40 years or 40 days.
The Flood - water flooded the earth for 40 days. (Genesis 7:17)
Moses was on Mount Sinai for 40 days and nights.
The Israelites wandered the desert and ate manna for 40 years. (Exodus 16:35)
Kings Saul, David, and Solomon reigned 40 years each.
Matthew 4:2 Jesus fasted for 40 days in the desert.
Acts 1:3 Jesus was on earth for 40 days after His resurrection.
The number 400 and 430
I know 400 isn't one of the frequent numbers, but several websites mentioned it. One source said the number 400 symbolizes in the Bible "a divine perfect time period." I don't know about that. I didn't find this source to be reliable on some other things so I am a bit skeptical. But when I teach on the historical time periods I talk about the 400 years the Israelites were in slavery in Egypt. And Exodus 12:40 tells us the time between when they entered Egypt and left was 430 years. Most references say the Intertestamental Period called The Silent Years - the time period between the Old Testament and New Testament when God prepared the fullness of time for Jesus to be born - was about 400 years. When you actually look at the dates it was more like 430 years.
Here is what always strikes me about that. We read that amount of time and it doesn't really register in our minds. 400 years or 430 years - well, either is a really long time to wait for something to happen, for God to intervene like when they were in slavery and God was preparing a great nation; or for God to prepare the fullness of time for the Messiah to come. See we think we should see God working. We think we should see the benefit of our faithfulness, our obedience, our service to the Lord right now, or at least in our lifetime. We want solutions and answers right now. We make it about me, me, me. But what if what I am doing right now or the total of my life impacts the generations to come in some way I can't see? What I do today may have some significance that I can't even fathom in this minuscule mind of mine. Or the whole point may have been to just live a life that glorifies God. Our viewpoint is so limited and temporal. But the biblical example of historical time is that hundreds of years can go by between significant events.
I used to give a lot of thought to the End Times. It seems like with all that is going on in the world right now, people are saying we are in them. But then I think about the horrific things that have gone on in the centuries before us when certainly people must have thought 'this is the end'; and God's chosen people being in slavery for 400 years. 400 years! How horrific that must have been and how easy it would have been to give up hope. How many generations would have come and gone! And where was God during that time? He was preparing the "time" for the next big thing. For His plan for history to come to fruition. (70 and their families went into Egypt and almost 2 million came out.) When I wrapped my head around that - the smallness of my life compared to the big picture - I gave up dwelling too much on the End Times. Instead I try to focus on making my life matter in the time I am given.
(Boy did I diverge from frequency of numbers in the Bible with that one! But the point is when reading the Bible you should recognize the long amount of times between historical big events and in preparation for God to use an individual or a nation.)
I wouldn't get obsessed with the frequency of various numbers in the Bible. I wouldn't read into the text something that might not be significant. However, it is interesting to note as you read the Bible that you do see certain numbers more often than others.
Kind of a trivia knowledge thing.
And if you are playing Bible Trivia and have to guess a number - 3, 7, 10, 12 and 40 seem to be good guesses. Ha.