The image of the birds as the nations of the world is also found in the Old Testament, as in Ezekiel 17:23’s messianic oracle. The mustard-plant image shows that from a tiny beginning, the kingdom will, by the life that works within it, grow into something greater than the powers of the world. The parable stresses the tiny outset and the gathering of all nations at the end rather than the intermediate growth. While these outcomes are not seen in Jesus’ earthly walk, he prophesies what will surely come to pass, even though it contradicts the expectations of his own day.
The birds represent the nations of the world.1 This final image of the parable of the mustard seed is also found in several places in the Old Testament—for example, the messianic oracle in Ezekiel 17:23. By means of the mustard-plant image, the parable teaches us that the kingdom of heaven will spring from a very small, unexpected beginning and, by the life that works within it, expand into something great that surpasses the powers of the world. One might say the parable highlights chiefly the tiny outset and the vast consummation of all nations at the end of history rather than the intermediate growth. These outcomes are not yet visible in Jesus’ earthly walk though. Yet he prophesies what will surely come to pass, even though it contradicts the hopes and expectations of his own day.2
32 It is the smallest of all seeds, but when it has grown it is larger than all the garden plants and becomes a tree, so that the birds of the air come and make nests in its branches.”