My doctrine shall drop as the rain, my speech shall distil as the dew, as the small rain upon the tender herb, and as the showers upon the grass: My doctrine - לקחי likchi, from לקח lakach, to take, carry away; to attract or gain over the heart by eloquence or persuasive speech.
Hence the Septuagint translate the word αποφθεγμα, an apophthegm, a sententious and weighty saying, for the regulation of the moral conduct such, properly, are the sayings in this inimitable ode.
Shall drop as the rain - It shall come drop by drop as the shower, beginning slowly and distinctly, but increasing more and more till the plenitude of righteousness is poured down, and the whole canon of Divine revelation completed.
My speech shall distil as the dew - אמרתי imrathi; my familiar, friendly, and affectionate speeches shall descend gently and softly, on the ear and the heart, as the dew, moistening and refreshing all around. In hot regions dew is often a substitute for rain, without it there could be no fertility, especially in those places where rain seldom falls. And in such places only can the metaphor here used be felt in its perfection. Homer uses a similar figure when speaking of the eloquence of Ulysses; he says, Il. iii., ver. 221: -
Αλλ' ὁτε δη ῥοπα τε μεγαλην εκ στηθεος ἱει,
Και επεα νιφαδεσσιν εοικοτα χειμεριῃσιν -
"But when he speaks what elocution flows!
Soft as the fleeces of descending snows."
On the manner in which dew is produced, philosophers are not yet agreed. It was long supposed to descend, and to differ only from rain as less from more; but the experiments of a French chemist seemed to prove that dew ascended in light thin vapours, and that, meeting with a colder region of the air, it became condensed and fell down upon the earth. Other recent experiments, though they have not entirely invalidated the former, have rendered the doctrine of the ascent of dew doubtful. Though we know nothing certain as to the manner of its production, yet we know that the thing exists, and that it is essentially useful. So much we know of the sayings of our God, and the blessed effects produced by them: God hath spoken, and the entering in of his words gives light and life. See the note on Genesis 2:6.
As the small rain - שעירם seirim, from שער saar, to be rough or tempestuous; sweeping showers, accompanied with a strong gale of wind.
And as the showers - רביבים rebibim, from רבה rabah to multiply, to increase greatly; shower after shower, or rather a continual rain, whose drops are multiplied beyond calculation, upon the earth; alluding perhaps to the rainy seasons in the East, or to those early and latter rains so essentially necessary for the vegetation and perfection of the grain.
No doubt these various expressions point out that great variety in the word or revelation of God whereby it is suited to every place, occasion, person, and state; being "profitable for doctrine, reproof, and edification in righteousness." Hence the apostle says that God, at sundry times and in divers manners, spake in time past unto the fathers by the prophets, and in these last times has spoken unto us by his Son; Hebrews 1:1, Hebrews 1:2. By every prophet, evangelist, and apostle, God speaks a particular language; all is his doctrine, his great system of instruction, for the information and salvation of the souls of men. But some portions are like the sweeping showers, in which the tempest of God's wrath appears against sinners. Others are like the incessant showers of gentle rain, preparing the soil for the germination of the grain, and causing it to take root. And others still are like the dew, mildly and gently insinuating convictions, persuasions, reproofs, and consolations. The preacher of righteousness who wishes to handle this word profitably, must attend closely to those distinctions, that he may rightly divide the word of truth, and give each of his hearers his portion of the bread of life in due season.