The strength of Jehovah over the earth will extend to Israel’s enemies, and they will be redeemed. In this case the redemption is from exile, and they will be gathered in. When they do, their righteousness will bring gladness and joy, contrasting with the conditions of their exile.
For Jacob, this is an important repetition of the theme of the gathering. Both Nephi and Jacob preach this gathering, something that doubtless was very important to them as they had been physically separated from Israel. For later prophets who had known no other home, the idea that they were in exile and would be gathered will fade from Nephite religious language.
Verses 12 through 15 return to the definition of who this god is. In verse 12 we have the phrase “son of man” which at times is applied to the Messiah. That is not the meaning here. Very clearly, the emphasis here is on the contrast between the permanence of Jehovah and the mortality of their enemies. It is a two-phase repetition of emphasis: “man, who shall die, and the son of man, who shall be made like unto grass.” The image of being made like unto grass refers to the grave. Hence, eternally constant Jehovah is contrasted with mortal enemies who will die, regardless of how powerful they are in this life.
Thus, in verse 13 Jehovah scolds Israel for fearing powerful enemies, when (in verse 14) Jehovah will release the captives.
In verse 15, the roaring of the waves poetically returns to the Jehovah who defeated Rahab and calmed the seas. Lord of Hosts is a way of saying that He is a god over all.