"And thus that Body of Christ becomes the leaven that steadily penetrates the whole of the worldly society, until the whole is leavened, (Matt 13:33), so that what began as a tiny mustardseed grows into the greatest of shrubs and and becomes a tree, so that the birds of the air come and make nests in the branches (Matt 13:31)." [1]
Theological reflection on GMA Jansen's image of leaven and mustardseed
Fr Jansen’s words draw deeply from Christ’s parables in Matthew 13, weaving together the imagery of leaven and mustard seed to describe the quiet yet transformative presence of the Body of Christ in the world. This passage is rich in meaning, particularly when understood in relation to the sacrament of baptism and the concept of co-existence within society.
The image of leaven suggests something hidden yet active. A small amount of yeast works invisibly through the dough, gradually transforming the whole. In the same way, through baptism, the individual is incorporated into the Body of Christ. This sacrament is not merely symbolic; it is transformative. The baptized person carries within them the life of Christ, and thus becomes part of this “leaven” in the world. The change may not always be dramatic or immediately visible, but it is real and ongoing.
Baptism, therefore, is not an isolated spiritual event. It places the believer within a living community - the Church - which is sent out into the world. Jansen’s insight is that the Body of Christ does not remain separate from worldly society, but exists within it, quietly permeating it. Christians live, work, and interact alongside others, and through their presence - shaped by grace - they contribute to the gradual transformation of society from within.
The second image, that of the mustard seed, reinforces this idea of organic, surprising growth. What begins as something small and seemingly insignificant becomes something expansive and life-giving. The “tree” that grows is large enough for “the birds of the air” to make their nests. This suggests not only growth, but hospitality and co-existence. The Church, formed through baptism, becomes a place where many can find shelter; including those who may not yet fully belong.
In terms of co-existence, this imagery is particularly powerful. It suggests that the Christian mission is not to dominate or withdraw from the world, but to dwell within it in a life-giving way. The baptized do not stand apart from society; rather, they are called to engage with it, to co-exist peacefully, and to influence it through love, justice, and truth. In the same way as the branches of the mustard tree, the Church extends outward, making room for others, fostering dialogue, and offering refuge.
Thus Jansen’s reflection highlights that through the sacrament of baptism, each Christian becomes part of a quiet but profound transformation of the world. The Kingdom of God does not arrive with force, but through steady, patient growth. It is a process of co-existence, where the sacred and the secular meet; not in conflict, but in a gradual movement toward renewal and unity.
Leaven and mustardseed
From but a mustard seed so small,
A tender shoot through earth did crawl;
By Hand of God, through sun and rain,
It rose through joy; it rose through pain.
At first so slight, scarce seen by eye,
Yet reaching upward to the sky;
Its branches widened far and free,
Till shrub became a mighty tree.
There birds of every feathered wing
Found place to rest and sweetly sing;
Their little nests were safely laid,
Within the shelter of its shade.
The fragile eggs, the downy young,
Were guarded where the branches hung;
And when the storm winds fiercely cried,
Within that tree they safe abide.
Beneath its boughs the weary came,
The poor, the pilgrim, worn and lame;
The labourer laid his burden down,
And rested there from field and town.
The children gathered joyful near,
With smiling hearts untouched by fear;
For God had made that shelter broad,
A living sign of grace from God.
So too the Church of Christ shall be,
A living, sheltering, holy tree;
For we, His Body, called by grace,
Must bear His Love in every place.
As leaven hidden in the bread
Moves softly through the dough widespread;
So must Christ’s Mercy gently move
Through all the world with truth and love.
What once began so passing small
Shall, by God’s blessing, nourish all;
As Scripture tells in words sublime,
Still echoing through age and time.
The mustard seed by Heaven sown
Became more vast than men had known;
And birds of air came from afar
To nest beneath its branches fair.
Thus are we sent through Baptism’s grace
To bring God’s Light to every place;
To dwell with sister, brother, friend,
And serve in love until life’s end.
Not set apart in prideful way,
But walking humbly day by day;
Co-existing in peace and care,
Simon-bearing each other’s cross with prayer.
Lord, let our hearts be rich in Thee,
Like branches of that blessed tree;
Till all our thoughts and works proclaim:
“Deus Meu” - God’s holy Name.
Then may the weary find their rest,
And frightened souls within us nest;
Till all creation comes to see
The Kingdom growing silently.
[1] Fr G.M.A. Jansen. (Norbert Jansen OP). p 13, Pro Veritate Vol V No. 12. Baptism and Co-existence. 15 April 1967
https://sahistory.org.za/sites/default/files/archive-files/PvApr67.pdf
With thanks to sahistory.org.za
Image courtesy of ChatGPT with CN Whittle "Divine Blessing over the leafy tree"
