Isaiah 54-55

Isaiah 54
1-17 The Eternal Covenant of Peace

1-3 Rejoice, you who were barren; you will have more children than the married woman. Build a bigger tent, for your family will grow and take over the land. In the immediate context, this is a comfort to those in Babylonian captivity, for they have been squelched in Babylon. But when they return they will again prosper; their families will grow. I see it as a welcome to the Gentiles – those who are not physical offspring of Abraham and Sarah. It's a theme that begins at least back in Genesis 12 when God promises Abraham that in his seed all the nations of the earth will be blessed and extends into the letters of Paul to the Christians in the first century. Even today we see that more physical Gentiles than physical Jews have accepted Christ and his salvation.
4-8 Forget the shame of your youth, the disgrace of your widowhood, because your Maker is now your husband. Though I abandoned you for a while, I will now have compassion on you out of an everlasting love. Again, this can be applied both to the Hebrew nation in captivity and to the Gentiles whom God would accept, according to Romans 9:25: "As indeed he says in Hosea, "Those who were not my people I will call "my people,' and her who was not beloved I will call "beloved.' "
9-10 Just as I (God) swore in the days of Noah I would never again destroy the earth with a flood, so my covenant of peace will not be removed from you. This also addresses both physical and spiritual Israel, which includes those of physical Israel who accept Christ as the Messiah.
11-12 I am about to build a glorious house for you. This has to be understood in a spiritual context (much as heaven is described in physical terms in Revelation 21:19), because the rebuilt temple certainly did not have a foundation of sapphires.
13-14 Your children shall be taught by the LORD (see John 6:45); you shall be established in righteousness.
15-17 I will not take the part of your enemies; no weapon of man can destroy you. This is your heritage as my servants.

Isaiah 55
1-13 An Invitation to Abundant Life

1-5 Come, you thirsty and hungry, eat what is good: listen to me, and I will make an everlasting covenant with you. The covenant I had with my beloved David will be extended to all nations. In Jesus' words in John 6:35: "I am the bread of life. Whoever comes to me will never be hungry, and whoever believes in me will never be thirsty."
6-9 Familiar verses here: "Seek the LORD while he may be found...." and "For my thoughts are not your thoughts, nor are your ways my ways...."
10-11 As the rain and snow return to the heavens, so shall my word not return to me empty. It shall accomplish my purposes.
12-13 You shall go out in joy and come back in peace; the mountains and hills will sing, and the trees will applaud, cypress and myrtle will replace thorn and brier as a memorial to God. The righteousness of Christ will replace the consequences of sin, which was symbolized by thorns and briers in Genesis 3:18, after the sin of Adam and Eve.