Matthew 13:31,32- Another parable put he forth unto them, saying, The kingdom of heaven is like to a grain of mustard seed, which a man took, and sowed in his field: Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof.
Here, the parable is used for the Kingom of heaven, however, in Luke it is used for the Kingdom of God.
Luke 13:18,19- Then said he, Unto what is the kingdom of God like? and whereunto shall I resemble it? It is like a grain of mustard seed, which a man took, and cast into his garden; and it grew, and waxed a great tree; and the fowls of the air lodged in the branches of it.
These two kingdoms are different. The kingdom of God is a spiritual kingdom. The kingdom of heaven is a literal, physical kingdom. When Christ was present on the earth, so were both kingdoms.
Notice that in Matthew the seed is sown in the field, and in Luke it is sown in a garden- showing once again that careful attention to the words of God will show a difference between the two kingdoms!
A mustard seed is associated with faith.
Matthew 17:20- And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.
The field is the world.
Matthew 13:38- The field is the world; the good seed are the children of the kingdom; but the tares are the children of the wicked one;
This man has misplaced his faith. He put it in the things of the world. And, when sight fails and things go badly, as they so often do, then his faith will waiver because it was never in something that would last!
Luke 18:8- I tell you that he will avenge them speedily. Nevertheless when the Son of man cometh, shall he find faith on the earth? This makes it clear that there will be little of true faith on the earth at the coming of Christ.
True faith as a grain of mustard seed, is classified as an herb. But, the mustard seed in this parable grows wild until it is no longer an herb, but it becomes a tree. Birds don't roost in mustard plants, they set up their homes in trees. Birds (unclean spirits) lodging in the branches shows that it is a bad tree- Ezekiel 31.
The standard interpretation is that the tree is the church, offering a haven of rest for all. It is the exact opposite. In fact, if coupled with the next parable, it is the Roman Catholic monstrosity, which offers a worldly faith which is "for the birds".
Revelation 18:1,2- And after these things I saw another angel come down from heaven, having great power; and the earth was lightened with his glory. And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.
A side note: the graven images, known as saints, which are in Catholic churches worldwide are placed in settings called Niches. The root of "niche" is Latin- nidus' meaning "Nest".
What about Luke 13?
Song Of Solomon 5:1- I am come into my garden, my sister, my spouse: I have gathered my myrrh with my spice; I have eaten my honeycomb with my honey; I have drunk my wine with my milk: eat, O friends; drink, yea, drink abundantly, O beloved.
Song Of Solomon 6:2- My beloved is gone down into his garden, to the beds of spices, to feed in the gardens, and to gather lilies.
The church is likened to a garden (see also Song Of Solomon 4). Christ and the church have a fellowship in the garden. It is delicate and fragile (Song of Solomon 5:1-7).
Our garden can be a sweet place of fellowship and blessing, but it can also be the place where we tell Christ "no". It was in a garden that man's fellowship with God was first broken. The twelve disciples forsook Christ in a garden after sleeping instead of praying(while men slept, his enemy came- Matthew 13:25).
Christ's borrowed tomb was in a garden. Christ chose the setting of a garden as the place to show the world that He triumphed over death.
Your garden can become your resting place, your triumphant place, or even your forsaking place. Be very careful not only where you plant your seed of faith, but also how you cultivate it!
