The earth produces by itself, first the blade, then the ear, then the full grain in the ear.
The lessons which our Saviour designs to teach us here by parables and figurative expressions are these: - I. That those who are good ought to consider the obligations they are under to do good; that is, as in the parable before, to bring forth fruit.
Commenting on Mark 4:21-34
And with many such parables,.... As those of the tares, of the leaven in three measures of meal, of the treasure hid in the field, the pearl of great price, the net cast into the sea, and of the Scribe instructed unto the kingdom of God; which though not related at length here, are by the Evangelist Matthew, in Mat 13:24 together with others elsewhere...
Verse 28. For the earth bringeth forth fruit of herself. That is, it is done without the power of man. It is done while man is engaged in other things. The scope of the place does not require us to suppose that our Saviour meant to say that the earth had any productive power of itself, but only that it produced its fruits not by the power of man.