Deuteronomy 32:2

Ver. 2. My doctrine shall drop as the rain— That is, As the rain which falls upon the earth is ordained to fertilize and nourish the plants and animals, so the heavenly doctrine, proceeding from God himself, is proper to open the understanding, soften the heart, and produce the most happy fruits. This metaphor is frequently used in Scripture, as well as in prophane authors. See Job 29:22.Isaiah 45:8; Isaiah 55:10. Proverbs 25:14 and Homer, Iliad. 3: ver. 222. The corresponding clause is, my speech should distil as the dew, which is considered as the especial cause of fertility, or of the perfection of the fruits of the earth. Nor is this a merely popular opinion. Dew, is not simple and crude water; it is water which has circulated through the tubes of plants, and which is itself impregnated with those most pure and subtile nutritive particles, which have evaporated through the pores of plants. This is Mr. Scheuchzer's observation. One would wonder that any commentators should so little feel the poetic energy of this passage, as to assert, that it should be rendered, let my doctrine drop as the rain; as if it were a prayer, not a beautiful and emphatical assertion, worthy the fine apostrophe in the 1st verse.