Look what effect rain and dew have upon herbs and grass, which they make fresh and fragrant and growing, the same effect I may justly expect and hope that my discourse will have upon your hearts, i.e. to make them soft and pliable and fruitful. Or this may be a prayer, Let my doctrine drop, &c. Oh that it might do so, that my discourse might not be lost upon you, but be profitable to you! the future tense of the indicative mood being put for the imperative mood, as is usual.
Related Commentaries of Deuteronomy 32:2
Deuteronomy 32:2
2 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: