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 this passage 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." God gives it its power. It has no power of its own. So religion in the heart is not by the power of man. It grows he cannot tell how, and of course he cannot without divine aid, control it. It is by the power of God. At the same time, as without industry man would have no harvest, so without active effort he would have no religion. Both are connected with his effort; both are to be measured commonly by his effort Philippians 2:12; both grow he cannot tell how; both increase when the proper means are used, and both depend on God for increase.
First the blade - The green, tender shoot, that first starts out of the earth before the stalk is formed.
Then the ear - The original means the stalk or spire of wheat or barley, as well as the ear.
The full corn - The ripe wheat. The grain swollen to its proper size. By this is denoted, undoubtedly, that grace or religion in the heart is of gradual growth. It is at first tender, feeble, perhaps almost imperceptible, like the first shootings of the grain in the earth. Perhaps also, like grain, it often lies long in the earth before there are signs of life. Like the tender grain, also, it needs care, kindness, and culture. A frost, a cold storm, or a burning sun alike injure it. So tender piety in the heart needs care, kindness, culture. It needs shelter from the frosts and storms of a cold, unfeeling world. It needs the genial dews and mild suns of heaven; in other words, it needs instruction, prayer, and friendly counsel from parents, teachers, ministers, and experienced Christians, that it may grow, and bring forth the full fruits of holiness. Like the grain, also, in due time it will grow strong; it will produce its appropriate fruit - a full and rich harvest - to the praise of God.

Bringeth forth - of herself - Αυτοματη. By its own energy, without either the influence or industry of man. Similar to this is the expression of the poet: -
Namque aliae, Nullis Homlnum Cogentibus, ipsae
Sponte Sua veniunt.
Virg. Geor. l. ii. v. 10
"Some (trees) grow of their own accord, without the labor of man."
All the endlessly varied herbage of the field is produced in this way.
The full corn - Πληρη σιτον, Full wheat; the perfect, full-grown, or ripe corn. Lucian uses κενος καρπος, Empty fruit, for imperfect, or unripe fruit. See Kypke.
The kingdom of God, which is generated in the soul by the word of life, under the influence of the Holy Spirit, is first very small; there is only a blade, but this is full of promise, for a good blade shows there is a good seed at bottom, and that the soil in which it is sown is good also. Then the ear - the strong stalk grows up, and the ear is formed at the top; the faith and love of the believing soul increase abundantly; it is justified freely through the redemption that is in Christ; it has the ear which is shortly to be filled with the ripe grain, the outlines of the whole image of God. Then the full corn. The soul is purified from all unrighteousness; and, having escaped the corruption that is in the world, it is made a partaker of the Divine nature, and is filled with all the fullness of God.

For the earth bringeth forth fruit (i) of herself; first the blade, then the ear, after that the full corn in the ear.
(i) By a certain power which moves itself.

For the earth bringeth forth fruit of herself,.... Without any further help, or cultivation from the husbandman; though under the influence of the sun, dews, and showers of rain from heaven: this is said, not to denote that man of himself, upon hearing the word, can bring forth the fruit of grace in himself; he cannot regenerate himself, nor quicken, nor convert himself; he cannot believe in Christ, nor love the Lord of himself; nor repent of his sin, nor begin, or carry on the good work; he can neither sanctify his heart, nor mortify the deeds of the body; or even bring forth the fruits of good works, when converted. For all these things are owing to the Spirit, power, and grace of God: men are regenerated according to the abundant mercy of God, of water and of the Spirit, by the word of truth, through the sovereign will and pleasure of God; and they are quickened, who before were dead in trespasses and sins, and were as dry bones, by the Spirit of God breathing upon them: conversion in the first production, is the Lord's work; "turn thou me, and I shall be turned": faith in Christ is not of ourselves, it is the gift of God; and so is repentance unto life; love is one of the fruits of the Spirit, and in short, the whole work of grace is not by might, nor by power of man, but by the Spirit of the Lord of hosts; who begins and carries on, and performs it until the day of Christ: the work of sanctification, is therefore called the sanctification of the Spirit; and it is through him the deeds of the body are mortified: and indeed, without Christ, believers themselves can do nothing at all; even cannot perform good works, or do any action that is truly and spiritually good. But the design is to show, that as the earth without human power, without the husbandman, under the influence of the heavens, brings forth fruit; so without human power, without the Gospel minister, the word having taken root under divine influence, through the sun of righteousness, the dews of divine grace, and operations of the blessed Spirit, it rises up and brings forth fruit:
first the blade, then the ear, after that the full corn in the ear; which, as it very aptly describes the progress of the seed from first to last; so it very beautifully represents the gradual increase of the work of grace, under the instrumentality of the word, accompanied with the Spirit and power of God. Grace at first appearance is very small, like the small green spire, when it first shoots out of the earth: light into a man's self, his heart, his state and condition, in the knowledge of Christ, and the doctrines of the Gospel, is but very small; he is one of little faith, and weak in the exercise of it: faith is but at first a small glimmering view of Christ, a venture upon him, a peradventure there may be life and salvation for such an one in him; it comes at length to a reliance and leaning upon him; and it is some time before the soul can walk alone by faith on him: its experience of the love of God is but small, but in process of time there is a growth and an increase; light increases, which shines more and more unto the perfect day; faith grows stronger and stronger; experience of the love of God is enlarged; and the believer wades in these waters of the sanctuary; not only as at first up to the ankles, but to the knees and loins; when at length they are a broad river to swim in, and which cannot be passed over.

For the earth bringeth forth fruit of herself; first the blade, then the ear, after that the full corn in the ear--beautiful allusion to the succession of similar stages, though not definitely marked periods, in the Christian life, and generally in the kingdom of God.

First the blade. There is a law of orderly development in natural growth, so also is it in reference to spiritual growth. Compare 1-John 2:12-14. Some growths are quicker than others, but in all there is growth. And we have no right to look for the end at the beginning, the ripened Christian experience in the young convert, the full corn in the first appearance of the blade. Observe, too, that we can know that there is growth by its results, though we know not how, and that each stage of the growth is more apparent than the preceding stage.