Observe that, by means of the grain of mustard seed in the parable, the heavenly doctrine is denoted which is sown like seed in the world, as in a field, [seed] which has an inherent force, fiery and powerful. For the Judge of the whole world is thus proclaimed, who, having been hidden in the heart of the earth in a tomb for three days, and having become a great tree, has stretched forth His branches to the ends of the earth. Sprouting out from Him, the twelve apostles, having become fair and fruitful boughs, were made a shelter for the nations as for the fowls of heaven, under which boughs, all having taken refuge, as birds flocking to a nest, have been made partakers of that wholesome and celestial food which is derived from them.
Reproduced in full. Translation: Ante-Nicene Fathers, vol. 1 (Roberts and Donaldson, 1885), public domain (Public domain).