He sendeth out his word - He commands: or, he speaks.
And melteth them - Melts the snow and the ice. Compare the notes at Job 37:10-12 : “By the breath of God frost is given,” etc. The idea is, that they are entirely under his control. They obey him when he speaks.
He causeth his wind to blow - The warm south wind: “his” wind, because he directs it, and causes it to perform his will.
And the waters flow - The snow and the ice melt.