Mustard (σίναπι, Mt 13:31; Mt 17:20; Mr 4:31; Lu 13:19; Lu 17:6; in Talmudic Chaldee חִרדָּל, chardal, Mishna, Shabb. 20:2, from the Syriac chardal,), a well-known pod-bearing shrub-like plant (genus Sinapis, of thirteen species, five of which are indigenous in Egypt, Descript. de l'Egypte, 19:96) that sometimes grows wild, and at other times is raised from the seed, which is employed as a condiment, being usually of the two kinds, the black and the white (see Penny Cyclopcedia, s.v. Sinapis). The Jews likewise cultivated mustard in their gardens (Mishna, Maaser. 4:6). The round kernels (Mt 13:31; Mt 17:20), which were used also by the ancients as a spice (Pliny, 19:54), passed in Jewish phrase as an emblem for a small, insignificant object (Buxtorf, Lex. Talm. col. 822); being the smallest seed commonly gathered in Palestine, although not literally the most diminutive known. "The Lord in his popular teaching," says Trench (Notes on Parables, page 108), "adhered to the popular language" (see also the Koran, Sur. 31). The statements in Mt 13:32, that when fully grown it is the greatest of plants, and becomes a tree under which the fowls may find shelter, has been supposed to indicate a larger growth than ordinary in Western countries (see Margrave, Hist. nat. Brasil. Page 291; Bauhin, Hist. Plant. 2:855); but is confirmed by the statements of the Talmudists, one of whom describes it as a tree of which the wood was sufficient to cover a potter's shed (Talm. Hieros. Peah, 7:4), and another says that he was wont to climb into it, as men climb into a fig-tree (ib. Ketuboth, fol. 3:2; comp. Rosenmuller, Alterth. 4:105). Mr. Buckham (On the Mustard-tree of the Scriptures, 1829) cites the following from Alonzo de Orvallo's Travels in Chili (as given in Awnshaw and Churchill's Collection): "The mustard-plant thrives so rapidly that it is as big as one's arm, and so high and thick that it looks like a tree. I have travelled many leagues through mustard-groves which were taller than horse and man; and the birds built their nests in them as the Gospel mentions." The statement of Irby and Mangles has also been referred to (Lambert, in the Linncean Transactions, 17:450), that they found the mustard-plant (Sinapis nigra) growing wild between Beisan and Ajlun as high as their horses' heads. (See further in Celsii Hierobot. 2:253 sq.; Billerbeck, Flora class. page 172.) Prof. Hackett states that he was for a long time disappointed in his search for any specimens of the mustard answering to the requirements of the above texts of Scripture; but that while on his way across the plain of Akka, towards Carmel, he had the satisfaction of seeing a little forest-like field of these plants, in full blossom, from six to nine feet in height, with branches from each side of a trunk an inch or more thick; and that he actually witnessed the alighting of birds upon the stems (Illustra. of Script. Page 124). Dr. Thomson also (The Land and the Book, 2:100) says that he has seen the wild mustard on the rich plain of Akkar as tall as the horse and the rider.
Even these descriptions, however, seem hardly to come up to the ancient accounts of the plant in question. Hence the conclusion of Dr. Royle (in a paper read before the Royal Asiatic Society, March 16, 1844) has been preferred, who shows that there is a plant still known in the East by the name of khardal (which corresponds to the rabbinical title, and is indeed the modern Arabic for "mustard"), growing near Jerusalem, but most abundantly on the banks of the Jordan and round the sea of Tiberias; its seed being employed as a substitute for mustard. The plant is the Salvadora Persica of Linnaeus (the Cissus' arborea of Forskal), a large shrub, or tree of moderate size, a native of the hot and dry parts of India, of Persia, and of Arabia. Dr. Roxburgh (Flor. Ind. 1:389 sq.) describes the berries as much smaller than a grain of black pepper, having a strong aromatic smell, and a taste much like that of garden cresses. The plant has a small seed, which produces a large tree with numerous branches, in which the birds of the air may take shelter. It is probably the tree which Irby and Mangles themselves suppose to be the mustard-tree of Scripture, rather than the ordinary shrub. They met with it while advancing towards Kerak, from the southern extremity of the Dead Sea. It bore its fruit in bunches resembling the currant; and the seeds had a pleasant, though strongly aromatic taste, nearly resembling mustard. A specimen of the tree had been brought home by Mr. W. Barker, and it had been ascertained by Messrs. Don and Lambert to be the Salvadora Persica of botanists; but both had written against its claim to be the mustard-tree of Scripture, while Mr. Frost, hearing a conversation on the subject, had supposed the tree to be a Phytolacca, and had hence maintained it to be the mustard-tree of Scripture, but without adducing proofs of any kind (Remarks on the Mustard-tree of the N.T. [Lond. 1827]; Bulletin des sciences nat. Mai, 1826, page 74; Journal of the Royal Asiatic Society, ut sup.).
On the other hand, "Hiller, Celsius, Rosenmiiller, who all studied the botany of the Bible, and older writers, such as Erasmus, Zezerus, Grotius, are content to believe that some common mustard-plant is the plant of the parable. The objection commonly made against any Sinapis is that the seed grew into 'a tree' (δένδρον), or, as Luke has it, 'a great tree' (δένδρον μέγα), in the branches of which the fowls of the air are said to come and lodge. Now, in answer to the above objection, it is urged with great truth that the expression is figurative and Oriental, and that in a proverbial simile no literal accuracy is to be expected; it is an error, for which the language of Scripture is not accountable, to assert, as Dr. Royle and some others have done, that the passage implies that birds 'built their nests' in the tree; the Greek word κατασκηνόω has no such meaning, the word merely means 'to settle or rest upon' anything for a longer or shorter time; the birds came, 'insidendi et versandi causa,' as Hiller (Hierophyt. 2:63) explains the phrase; nor is there ally occasion to suppose that the expression 'fowls of the air' denotes any other than the smaller insessorial kinds-linnets, finches, etc. and not the 'aquatic fowls by the lake-side, or partridges and pigeons hovering over the rich plain of Genesareth' which Prof. Stanley (S. and P. page 427) recognises as 'the birds that came and devoured the seed by the way-side' — for the larger birds are wild and avoid the way-side — or as those 'which took refuge in the spreading branches of the mustard-tree.' Hiller's explanation is probably the correct one; that the birds came and settled on the mustard-plant for the sake of the seed, of which they are very fond. Again, whatever the aivant may be, it is expressly said to be an herb, or, more properly, 'a garden herb' (λάχανον, olus). As to the plant being called a 'tree' or a 'great tree,' the expression is not only an Oriental one, but it is clearly spoken with reference to some other thing; the σίναπι, with respect to the other herbs of the garden, may, considering the size to which it grows, justly be called 'a great tree,' though, of course, with respect to trees properly so named, it could not be called one at all. Now it is clear from Scripture that the σίναπι was cultivated in our Lord's time, the seed a 'man took and sowed in his field;' Luke says, 'cast into his garden:' if, then, the wild plant on the rich plain of Akkar grows as high as a man on horseback, it might attain to the same or a greater height when in a cultivated garden; and if, as lady Callcott has observed, we take into account the very low plants and shrubs upon which birds often roost, it will readily be seen that some common mustard-plant is able to fulfil all the scriptural demands. As to the story of the rabbi Simeon ben-Calaphtha having in his garden a mustard-plant into which he was accustomed to climb as men climb into a fig-tree, it can only be taken for what Talmudical statements generally are worth, and must be quite insufficient to afford grounds for any argument. But it may be asked, Why not accept the explanation that the Salvadora Persica is the tree denoted?-a tree which will literally meet all the demands of the parable. Because, we answer, where the commonly received opinion can be shown to be in full accordance with the scriptural allusions, there is no occasion to be dissatisfied with it; and again, because at present we know nothing certain of the occurrence of the Salvadora Persica in Palestine, except that it occurs in the small tropical low valley of Engedi, near the Dead Sea, whence Dr. Hooker saw specimens, but it is evidently of rare occurrence. Mr. Ameuny says he had seen it all along the banks of the Jordan, near the lake of Tiberias and Damascus; but this statement is certainly erroneous.
We know from Pliny, Dioscorides, and other Greek and Roman writers, that mustard-seeds were much valued, and were used as a condiment; but it is more probable that the Jews of our Lord's time were in the habit of making a similar, use of the seeds of some common mustard (Sinapis) than that they used to plant in their gardens the seeds of a tree which certainly cannot fulfil the scriptural demand of being called 'a pot-herb."' Dr. Tristram likewise (Nat. Hist. of the Bible, page 472 sq.) takes strong ground in favor of the common black mustard and against the Salvadora Persica. See Kitto, Pict. Bible, note on Lu 17:6.