The seed of this plant is used proverbially for anything exceedingly small. In this sense it occurs in the Gospels (Mt 17:20 etc.), and in the Talmud (Buxtorf, Lex. s.v. 'Chardal'). Jesus compares the Kingdom of heaven to the mustard seed (Mt 13:31 etc.). The plant intended is the Sinapis nigra (Arabic khardal), which grows wild in Palestine, and is a familiar sight on the shores of Gennesaret. It is also found under cultivation, and in the gardens it reaches a great size, being often from 10 to 12 feet in height. An annual, growing from seed, it is naturally compared with other garden herbs, which, although it springs from the smallest seed, it quite outgrows. It bears a profusion of minute seeds, of which the birds are very fond, sitting ('lodging') on the branches as they eat. Although it is not properly' a tree' (Lu 13:19), it quite accords with Oriental use to describe as such a great plant like this.

W. Ewing.