There is nothing new under the sun, of course, so it shouldn't be surprising when we glean a pearl of wisdom from the Hebrew Bible despite it being written thousands of years ago. The particular pearl from the Old Testament which applies this week is found in the Book of Judges.

We read in chapter 12 about the defeat of the men of Ephraim, one of the tribes of Israel, by the men of Gilead. Once they had been beaten in battle, the remaining Ephraimites tried to cross the River Jordan. The men of Gilead instigated a test to root out the Ephraimites trying to sneak back home.

They ordered each man trying to cross to take a test. We read in verses five and six: 'Whenever one of the fugitives of Ephraim said, "Let me go over," the men of Gilead would say to him, "Are you an Ephraimite?" When he said, "No", they said to him, "Then say Shibboleth," and he said, "Sibboleth", for he could not pronounce it right. Then they seized him and killed him at the fords of the Jordan. Forty-two thousand of the Ephraimites fell at that time.'

Perhaps you see where this is going.

The word shibboleth has passed into contemporary English usage meaning a test applied to work out who is 'in' and who is 'out'. We may no longer put people to death if they fail our test of being the genuine article, but we still see these tests frequently.

We see them applied on behalf of the secular culture at large to people of faith. David Barclay, writing for the Christian think tank Theos, identified a 'progressive test' which is applied to people of faith before progressive liberals are prepared to work with them. He argues the latest to fall foul of this was Tim Farron, the Liberal Democrat leader who resigned citing disapproval of his evangelical faith and personal views on sexuality.

'When liberals insist on enacting strict "progressive tests" for anyone they might collaborate with,' argues Barclay, 'they undercut the very diversity they claim to champion. They also make it harder for people from very different traditions and worldviews to find a meaningful sense of solidarity and common purpose.'

The real tragedy is that it isn't just the secular world imposing these shibboleths on the Church though, but that groups within the Christian faith seem to apply them to each other.

We mark the 500^th anniversary of the beginning of the Reformation this year. This is probably the ultimate example in the Western Church of us creating 'in' and 'out' groups. Men were burned at the stake, on both sides, owing to their view of the Pope, communion, and justification.

These are, of course, important issues. How we are justified before God is a key component of Christian theology. The problem with making it a shibboleth is that when someone fails the test, we are obliged to kick them out of the group. At its worst, this has meant killing them.

Debates over baptism have been another cause of tests being applied. Anabaptists, who thought only adults could assent to being baptised were persecuted by their fellow Protestants – Zwingli even had the saintly Balthasar Hubmaier racked.

There are, of course, many more examples from the Reformation and Counter-Reformation. Let's bring it up to date, though. This week, the eminent pastor and Bible translator Eugene Peterson was quoted as approving of same sex marriage.

As soon as the news broke, he was condemned by thousands of conservatives on social media. I saw tweets suggesting his books be burned, while others claimed he'd never read a Bible. It was the shibboleth in action. Peterson, in suggesting there may be more than one interpretation of the Bible's view on sexuality had failed the test and was being cast out.

Awkwardly for those who'd already burned him at the stake of social media, Peterson then released a statement clarifying his views, which seemed to take a more conservative line. He'd been cast out of the circle too quickly.

Baptism, sexuality, communion and justification are vital issues and we need to talk about them. We can't just 'agree to disagree' and forget all about it – we've got to wrestle and debate. But let's not apply the shibboleth test too quickly. Who knows whether we would pass it ourselves if we had to cross the River Jordan today?

Follow Andy Walton on Twitter @waltonandy