This is a beautiful break in the Chapter, to call up even the inanimate parts of nature to celebrate, in sacred hymns, the glories of redemption: Heaven and earth shall sing of it, for both worlds take part in the triumphs of redeeming grace. Luke 2:13-14.
Related Commentaries of Isaiah 49:13
Isaiah 49:13
13 Sing, O heavens; and be joyful, O earth; and break forth into singing, O mountains: for the LORD hath comforted his people, and will have mercy upon his afflicted.