a grain of mustard seed

a grain of mustard seed

A small or seemingly insignificant thing that has the potential to grow or develop into something vast or formidable. Originating from the Parable of the Mustard Seed in the Bible (in the Gospels of Matthew, Mark, and Luke), describing how the Christian faith spreads and flourishes from small beginnings. Every child is a grain of mustard seed—at once relatively small in the scope of the world, but having within them the power to shape the very course of human existence.
See also: grain, mustard, of, seed

a grain of mustard seed

a small thing capable of vast development.
Black mustard seed grows to a great height. In Matthew 13:31–2 it is stated that ‘mustard seed…indeed is the least of all seeds: but when it is grown, it is the greatest among herbs’.
See also: grain, mustard, of, seed
References in classic literature ?
The duchess asked Sancho how he had fared on that long journey, to which Sancho replied, "I felt, senora, that we were flying through the region of fire, as my master told me, and I wanted to uncover my eyes for a bit; but my master, when I asked leave to uncover myself, would not let me; but as I have a little bit of curiosity about me, and a desire to know what is forbidden and kept from me, quietly and without anyone seeing me I drew aside the handkerchief covering my eyes ever so little, close to my nose, and from underneath looked towards the earth, and it seemed to me that it was altogether no bigger than a grain of mustard seed, and that the men walking on it were little bigger than hazel nuts; so you may see how high we must have got to then.
To this the duchess said, "Sancho, my friend, mind what you are saying; it seems you could not have seen the earth, but only the men walking on it; for if the earth looked to you like a grain of mustard seed, and each man like a hazel nut, one man alone would have covered the whole earth.
If ye have faith even as small as a grain of mustard seed, you will say to this mountain, "Move from here to there," and it will move and nothing will be impossible to you.