Mustard
Easton's Bible Dictionary 1897
A plant of the genus sinapis, a pod-bearing, shrub-like plant, growing wild, and also cultivated in gardens. The little round seeds were an emblem of any small insignificant object. It is not mentioned in the Old Testament; and in each of the three instances of its occurrence in the New Testament (Matt. 13:31, 32; Mark 4:31, 32; Luke 13:18, 19) it is spoken of only with reference to the smallness of its seed. The common mustard of Palestine is the Sinapis nigra. This garden herb sometimes grows to a considerable height, so as to be spoken of as “a tree” as compared with garden herbs.
Smith's Bible Dictionary 1863
International Standard Bible Encyclopedia 1915
mus'-tard (sinapi (Mt 13:31; Mr 4:31; Lu 13:19; Mt 17:20; Lu 17:6)): The minuteness of the seed is referred to in all these passages, while in the first three the large size of the herb growing from it is mentioned. In Mt 13:32 it is described as "greater than the herbs, and becometh a tree" (compare Lu 13:19); in Mr 4:32 it "becometh greater than all the herbs, and putteth out great branches." Several varieties of mustard (Arabic, khardal) have notably small seed, and under favorable conditions grow in a few months into very tall herbs--10 to 12 ft. The rapid growth of an annual herb to such a height must always be a striking fact. Sinapis nigra, the black mustard, which is cultivated, Sinapis alba, or white mustard, and Sinapis arvensis, or the charlock (all of Natural Order Cruciferae), would, any one of them, suit the requirements of the parable; birds readily alight upon their branches to eat the seed (Mt 13:32, etc.), not, be it noted, to build their nests, which is nowhere implied.
Among the rabbis a "grain of mustard" was a common expression for anything very minute, which explains our Lord's phrase, "faith as a grain of mustard seed" (Mt 17:20; Lu 17:6).
The suggestion that the New Testament references may allude to a tall shrub Salvadora persica, which grows on the southern shores of the Dead Sea, rests solely upon the fact that this plant is sometimes called khardal by the Arabs, but it has no serious claim to be the sinapi of the Bible.
E. W. G. Masterman