Come down, to wit, by the influences of his government upon his people under him. But this phrase doth much better agree to Christ, who was yet to come, and who did come down from heaven, and brought or sent down from heaven his doctrine, which is oft compared to rain, and the sweet and powerful influences of his Spirit. Rain upon the mown grass; which it both refresheth and improveth, or causeth to grow and flourish, and therefore was very acceptable, especially in Canaan, where rain was more scarce and more necessary than in many other places, because of the scorching heat, and the natural dryness of the soil, and the want of rivers to overflow or water the land.
Related Commentaries of Psalms 72:6
Psalms 72:6
6 He shall come down like rain upon the mown grass: as showers that water the earth.