When I was in theological college, we had a sermon class which was our weekly trial by ordeal. We would be given a text to preach on and expected to produce 20 minutes of Spurgeonic brilliance, no matter how obscure it was. Even after a good few years of experience, there are still texts that preachers probably prefer to avoid – though there's something in all of them, if we look hard enough.

1. Genesis 15: 9-21: When God made a covenant with Abram, he told him to cut in half a heifer, a goat and a ram and arrange the halves opposite each other, with a dove and a young pigeon. After that, "A smoking brazier with a blazing torch appeared and passed between the pieces" (17, NIV). It's all very mysterious, not to say bloody. The first thing to say is, don't try this at home: but it seems to be a dramatic way of illustrating the unbreakable covenant between God and Abram, with the divided animals – one half for each side of the deal – being symbolically welded back together with a supernatural flame.

2. Genesis 30: 25-43: This is the one where Jacob, who's still living with his father-in-law, hits on a wheeze to increase his flocks. He cuts a deal with Laban to let him have all the spotted sheep and goats for his wages. Jacob took tree branches, made stripes on them by peeling the bark and put them in front of the flocks when the animals mated. All the offspring were speckled, and he got rich thanks to his innovative breeding programme. There are plenty of historical examples of pregnancy superstitions: in some cultures pregnant women shouldn't look into a fire because their child will be born with a rash on its face, or beat a dog because their child will bark, or sit in a doorway because the baby will get stuck, or look at anything ugly because the baby will be ugly. This seems to belong to the same family of beliefs, though conservative Christians will want to highlight God's miraculous intervention.

3. 2 Kings 6: 1-7: The prophet Elisha was out with some other prophets one day and one of them lost an iron axe-head in a river. Elisha cut a stick, threw it into the water at the same place and the axe-head floated. A very useful prophet to have around, Elisha. But what's going on? It seems to be an example of an acted prayer, in which a desired result is mimicked, with a miraculous result: just as the stick floats, so does the axehead. Elijah did the same when he prayed for rain with his head between his knees, imitating the shape of a cloud (1 Kings 18:42) and when he raised the son of the widow of Zarephath (1 Kings 17:21). Becoming what we pray for – there's a sermon in that.

4. Numbers 22: 21-31: Balaam the prophet is ordered to curse the Israelites, and as he's on the way to do it his donkey stops in the middle of the road. He beats it to get it to move, and it tells him off, whereupon he flies into a rage: "You have made a fool of me! If I had a sword in my hand I would kill you right now." Someone's said that the amazing thing isn't that the donkey spoke, but Balaam had the presence of mind to answer. Never despise wisdom, even from the most unlikely sources; the chances are that you're the donkey, not the person you get angry with.

5. Acts 20: 7-12: Preachers don't like this one because it strikes too close to home. Paul was preaching "on and on" one evening in an upstairs room, Luke says, and a young man named Eutychus fell asleep and fell to his death. Fortunately Paul was at hand to resurrect him. Every preacher should be forced to preach on this passage at least once, preferably on a hot Sunday evening; it would keep us humble.

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