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In Luke, we read:

The apostles said to the Lord, “Increase our faith!” And the Lord said, “If you had faith like a grain of mustard seed, you could say to this mulberry tree, ‘Be uprooted and planted in the sea,’ and it would obey you.—Luke 17:5-6 (ESV)

Given the way Jesus used the imagery of the mustard seed, I assume that he always thinks of it as a symbol of something small yet full of potential. But I've been told:

There's actually a bit more to the mustard seed than size: a mustard seed is quite robust, very spicy, and of course, you can plant it and grow mustard.

These things are true, but would it be a valid interpretation of the text to say that Jesus suggests our faith should be like a mustard seed in terms of, say, robustness?

In other words, should we think of the mustard seed metaphor as a standard trope in Jesus' teaching?

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2 Answers 2

Jesus always uses the mustard seed to represent something small. The mustard seed was popularly known to be the smallest of all seeds.1 Of course, it also has the property of being a seed (i.e. it germinates), but that part of the metaphor is not unique to being a mustard seed. There is no record of Jesus using any other of the mustard seed's unique properties, like its spiciness, as a metaphor.

Jesus refers to the mustard seed in the following passages: Matthew 13:31-32, Matthew 17:20, Mark 4:31, Luke 13:19, and Luke 17:6.

In Matthew 13:31-32 and Mark 4:31, Jesus explicitly makes a comparison to the smallness of the seed. In both cases, the germination of the seed is also obviously in view. The seed becomes something: a kingdom represented by the tree. Luke 13:19 is a parallel saying to the ones in Matthew and Mark. While Jesus doesn't explicitly mention the smallness of the seed, the same idea is no doubt in view: what starts as a very tiny seed becomes something large.

That leaves Matthew 17:20 and Luke 17:6, which are saying very similar to one another. In both of these passages the size of the seed is important, but probably the fact that it is a seed is not.

The passage in Luke 17:6 makes by far the most sense if the analogy is to the seed's size. The disciples ask Jesus to increase their faith. An exchange in which he replies, "If your faith was spicy like a mustard seed..." or, "If your faith was robust like a mustard seed..." makes little sense. The conversation essentially becomes the apostles saying , "Increase our faith." and Jesus replying "Yeah, faith is great." It makes much more sense as a rebuke: the apostles asking for an increase in faith, and Jesus explaining that the amount of one's faith is not the locus of power.

Matthew 17:20 is so similar to the rest, it would be hard to believe that Jesus has anything in mind other than the size of the seed. His constrast is to the "faithless and twisted generation" in verse 17, suggesting, again, that his point is that faith is a matter of presence rather than size. Even if an alternate reading is semantically possible, there is nothing from the context to recommend one.

1 Bock, Darrell (BECNT)

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This seems in line with "everything characterized by a mustard seed is 'small'." An interesting follow-up would be to answer the question "is everything small, in Jesus' teachings, described by 'mustard seed?'" –  swasheck Jul 6 '12 at 14:19
@swasheck Mathew 7:5 - You hypocrite, first take the plank out of your own eye, and then you will see clearly to remove the speck from your brother's eye. –  philosodad Jul 7 '12 at 5:24
excellent addition. context really is important, isn't it? –  swasheck Jul 10 '12 at 16:16
Many commentators disagree with this assessment, as an example: barnes.biblecommenter.com/matthew/17.htm, which says, in part: "There is a principle of vitality in the grain of seed stretching forward to great results, which illustrates the nature of faith. Your faith should be like that. This is probably the true meaning." –  philosodad Jul 11 '12 at 0:52

No. Yes, mustard seeds are small, but that isn't their only important property. Jesus doesn't say "If you had faith like a tiny grain of sand", or "The kingdom of heaven is like something really small". He uses the image of a tiny speck of dust, a "mote" when describing something really tiny in another passage, so it isn't like the mustard seed is the only tiny image he's got on hand. By choosing a mustard seed, he is picking something that is insignificant in the wrong environment and immensely powerful, even disruptive, in the right one.

In the parable of the mustard seed, Jesus compares the Kingdom of Heaven to a mustard seed planted in a field or garden. The size of the seed is a part of this metaphor—no one is denying that—but the fact that it is a seed is the bulk of the metaphors power. If the kingdom of heaven were not like a seed or some other transformative thing, it would stay small!

But there's also the characteristics of the mustard plant to take into account.

From wikipedia (citing a more reliable source)

There is a "subversive and scandalous"[6] element to this parable, in that the fast-growing nature of the mustard plant makes it a "malignant weed"[6] with "dangerous takeover properties".[6]

It makes no sense to interpret this as being about the size of the seed but ignore the other "subversive and scandalous" properties. Is it good to have a giant mustard bush in your field? Is it good to have birds sheltering in its branches? What about the other plants in the field—birds are known for eating crops and shade isn't always a good thing.

If you read Acts, you read about people giving away all of their goods and abandoning their homes to partake of the Kingdom of Heaven and about how this totally messed with the power structure of the time and made them really upset—like they would be if a mustard seed got in the garden.

That's spicy faith, not bland faith, and robust faith, not weak.

If we ignore all the other properties of a mustard seed and the mustard plant, and say that this parable is only about size, we're reducing—without reason—the levels of metaphor that a passage from the Bible contains and reducing the power of a metaphor to one that is comfortable and easily accepted.

Looking at the concept, again, of the apostles asking Jesus to increase their faith and his reply, if we focus on size alone Jesus is saying: If you had even a little tiny bit of faith, regardless of it's character or properties, you could move mountains.

But again, Jesus doesn't choose something that isn't a seed to illustrate his point. He doesn't use a grain of sand, although a grain of sand is also small. So why choose a mustard seed? What properties does a mustard seed have that a grain of sand does not?

To focus only the size of the mustard seed and ignore its other properties is to assume that Jesus was speaking in shallow metaphors to people who didn't think very deeply about gardening, seeds, or mustard. That's not historically accurate or particularly complimentary to Jesus. It reduces a potent image rich in meaning to an obvious image with little to recommend it.

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Welcome to BH.SE! I think I understand your comment on P.SE a bit better now. Thank you particularly for citing Jesus And the Origins of the Gentile Mission by Michael F. Bird. It's a persuasive answer that I will need to ponder. Well done! –  Jon Ericson Jul 7 '12 at 17:14
Would those who voted this answer down please explain their reasons? I'm sure that if you want more citations or explanation, I would be happy to provide. –  philosodad Jul 12 '12 at 23:45

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