The number seven keeps on cropping up in the Bible. It's sometimes described as the 'perfect number', but it's not as simple as that: it isn't only used for 'good' things but for very bad ones too.

It first appears in Genesis 2. God has created the heavens and the earth in six days and on the seventh day he rested from all his work (verse 2). This pattern of work and rest is enjoined on the people of Israel too: every seventh day they have to rest.

The number seven seems to be ingrained in how the Israelites thought. Animals have to be at least seven days old before they can be sacrificed (Exodus 22:30), there are seven lamps on the lampstand of the tabernacle (Exodus 25:37) and Joshua has to march seven times round Jericho (for seven days).

But not all the uses of the word speak of holiness or the activity of God. In proverbs 26:24, the writer says of a malicious man: "Though his speech is charming, do not believe him, for seven abominations fill his heart."

In Luke 8:2 we read of Mary Magdalene, from whom seven demons had come out. And Jesus speaks of an evil spirit leaving a person then returning; finding its "house" unoccupied, "Then it goes and takes with it seven other spirits more wicked than itself, and they go in and live there" (Matthew 12:45).

The number is used often in the New Testament. Jesus tells Peter to forgive someone "seventy times seven" (Matthew 18:22) and in Revelation it occurs no less than 50 times. There are seven golden lampstands (1:12), seven stars (1:16), seven seals (5:1) and seven angels with seven trumpets (8:2), to name but a few. But what does this tell us about how to read the Bible?

1. It tells us not to take numbers too seriously

In our culture today, we are very exact about numbers. We expect accuracy, and it's easy to check. But in the biblical world, while of course sometimes exact numbers were very important, sometimes they were used as symbols rather than meaning exactly what they said. So when Proverbs says "seven abominations fill the heart" of a malicious person, that's a way of saying, "He is completely malicious" – we shouldn't try to imagine exactly what those abominations were. So we shouldn't try to over-interpret passages in Revelation or Daniel to give information about the Second Coming, for example.

2. It says there is order in the spiritual world

The repetition of the number seven encourages us to see patterns in how God engages with the world. Sometimes the biblical writers used this as a poetical or rhetorical devices, but sometimes it seems there's something about the number that corresponds to how things really are. So there are seven last sayings of Jesus on the cross, which we gather from the four different Gospels; that's not made up, it's real.

3. It reminds us God has left hints of his existence everywhere

Lots of different religions and philosphies see seven as some sort of sacred number. It's significant in Hinduism, Islam and of course Judaism. It's also important in astrology (traditionally there were seven planets). Even science and nature witness to it: Sir Isaac Newton identified seven colours of the rainbow. We even have seven days in a week.