It is like a grain of mustard seed
Both for its smallness at first, and its after increase; wherefore both the Evangelists Matthew and Mark observe, that it "is the least of all seed": which is true of the ministry of the Gospel, of the Gospel church state, and of the grace of God in the hearts of his people:
which a man took and cast into his garden;
the Ethiopic version renders it, "and sowed in his field", as in ( Matthew 13:31 ) though mustard used to be sowed in gardens as well as in fields. F24 Says R. Simeon ben Chelphetha, I have one stalk of mustard seed, (ylv dwtb) , "in my garden": so F25 Buxtorf translates it. And by the place in the text, where this seed is cast, may be meant, either the "field" of the world, where the Gospel is preached, and churches are raised; or the "garden" of the church, where the word and ordinances are administered, and in the hearts of the members of it, the grace of God is implanted and increased; see ( Song of Solomon 4:12 Song of Solomon 4:13 )
and it grew and waxed a great tree,
which may design the spread of the Gospel in the world, the flourishing state of the church of Christ, and the growth of grace in the hearts of believers.
And the fowls of the air lodged in the branches of it;
the Syriac version reads in the singular number, "the fowl of the air"; not Satan, and his principalities and powers, which devour the seed sown by the wayside; nor the angels of heaven; but rather gracious men on earth, who sit under the shadow of a Gospel ministry with great delight; and "make their nests", as the Persic version here renders the words, and take up their residence in Gospel churches; (See Gill on Matthew 13:31), (See Gill on Matthew 13:32), (See Gill on Mark 4:31), (See Gill on Mark 4:32).