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.

He sendeth out his word - He gives a command: the south wind blows; the thaw takes place; and the ice and snow being liquefied, the waters flow, where before they were bound up by the ice.

He sendeth out his word, and melteth them,.... The snow, the hoar frost, and ice: this he does by a word of his, who can freeze the earth and waters, and thaw them at his pleasure; by ordering the sun to break forth with great heat, or rain to fall in great plenty; of both which Kimchi interprets his word; as well as by causing a warm wind to blow, as follows,
he causeth his wind to blow, and the waters to flow: the south wind particularly; then the waters, which were still and motionless, flow as before, or more abundantly. Thus the hearts of men in a state of nature are like frozen earth or waters; they are cold, and without the heat of love, and affection to God and Christ, and spiritual things; they are as hard as a stone, and without any motion or desire after things divine and heavenly: but when the Lord sends his word, attended with a divine power and efficacy, it breaks and melts them; when the south wind of the blessed Spirit blows upon them, or his grace becomes effectual in convincing them of sin, righteousness, and judgment; and when the sun of righteousness arises on them with healing in his wings; with which being warmed, they are loosened, and flow to the Lord and his goodness for all spiritual blessings.