The two fibres in question are linen and wool, and they are mixed on two occasions: in the High Priest’s ephod (Exodus 28 & 39) and in the tabernacle’s curtain (Exodus 26)—which are the same thing, because the High Priest’s outfit marks him out as a walking, talking tabernacle. You can’t mix because mixing is a holy thing. Only the high priest wears a garment of mixed fibres. Only the tabernacle is woven with them. Only in God is mixing allowed. Which might help us think about the wisdom here: the Church of God is a holy place where mixing is allowed. 

When someone wants to point out that Christians don’t believe the Bible—often because they want to poke holes in a Christian sexual ethic—they turn to one of two places, mixed fibres or shellfish.

Both are laws from the old testament, one part of the food laws which I’ve written on before, the other one of those esoteric things which seems bizarre to us. All the Law was given for our instruction, though, so it must teach us.

Before considering what it might have to say to us, it’s worth pointing out the common gotcha—perhaps most famous in a scene in the West Wing—completely misunderstands how Christians have understood the Law. For all there is debate about exactly how we should think of these things, Christians have always thought carefully about how these things work and decided that some are to be kept and other understood as wisdom to us. It’s not a gotcha at all. It’s also worth drawing your attention to the way that sexual purity laws function differently in Leviticus to mixed fibres or food laws, they aren’t the same sort of thing—perhaps a topic for another time!

So, what are we meant to do with Leviticus 19’s prohibition on mixed fibres? It’s clustered with a law against breeding different kinds of animals together and a law against planting different kinds of seeds in a field. We should immediately think that the clustering is meant to make us notice something about not mixing with different ‘kinds.’

I’m sure we could jump to all sorts of conclusions which would be out of step with the Biblical witness, but it must have something to do with this.

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