The Flood

I. The Old World

The NT compares the days of Noah with the days of Christ (Matt. 24:36-37; Luke 17:26-27). It is essentially an old world judged with a flood; and a new world that will be judged with fire. Just like Noah was saved through the flood and because of the flood, God’s people will be saved through the fire in Christ.
John Owen (Biblical Theology) was one of the first to trace the events before the flood as prototypical for the events we see now. There are two seeds or lines that are different in worship and spirit. They were in a struggle between them and in the end, the demise of the world comes about when the two groups intermix. Gen. 6:1-7 does not teach some kind of intermingling of human race and angelic beings. This mixture is impossible in terms of how God made everything after its kind. There is no mention of the potential of procreation among the angels. In fact, the NT makes clear that after the resurrection, Christians will be like the angels, who cannot “be given in marriage” (Matt. 22:30). Moreover, the whole idea that such a union would have produced nephilim in the sense of oversized human beings is grammatically and exegetically impossible. The nephilim were already in existence before the supposed “union” (4). The nephilim, perhaps also physically imposing, yet more importantly, politically imposing in a totalitarian sort of way, accumulating to themselves power and wielding it dictatorially.  More on this here.
One of the things that marked the old world was the beautiful reformation of the people of God under Enoch, who walked with God, but also prophesied of judgment to come (see Jude). His ascension into heaven was a remarkable token that God would overcome death for His people.

II. The Flood

The revelation of the flood closes the pre-Flood period in redemptive history with an apocalyptic storm, which all but extinguishes the horizon of grace. Yet, this storm serves to show how divine blessing will only come in the way of just judgment upon sin, the wondrous preservation because of grace, and gracious salvation in the end (Gen 6:8 “Noah found grace in the eyes of the Lord“).
It is not only so that Noah and his family were saved from the water by the ark; according to 1 Pet. 3:20, they were saved by means of the water. So too, Peter says, baptism, that is, the answer of a good conscience (by grace) saves a person, by means of the resurrection of Christ (Rom. 6:4). This means that the water, which purged the earth of violence and corruption, saved this small company as they were in the ark. If they had simply been in the ark, but no water had come, the value of the ark would have been nil. The point is that while the whole world was destroyed by the Flood, at the same time that very water of the Flood separated the church from the wicked world. The wicked world threatened Noah, threatened either to swallow him up or to destroy him.” In the gospel, believers are saved by the death and resurrection of Christ, that is, when the waters went over his soul and the judgment of God was heavy upon him, God’s church was saved in the way of righteousness (Isa. 1:27). The prophets pick this up and show how this will happened also in the gospel (cf. Isa. 54:6-12).

III. The Bow in the Cloud

It is in conjunction with the flood, that the first explicit mention of the covenant appears. (introduced as “my covenantבְּרִיתִי Gen. 9:11; cf. Gen. 6:18). The way it is introduced makes clear that this covenant originated with God and preexisted its manifestation to Noah. The covenant here is God’s plan and promise granted freely and graciously, in a way that brings them into relationship to the Lord, under his special revelation and privileges, and includes some implications for all of creation.  See also Fairbairn.
The multi-colored bow in the cloud is the sign of the covenant, that guarantees God’s prospering of the world, maintaining it and fulfilling its purpose, in a way that God is committed to the long-term life of his people and creation. As Vos says so well: “The sign here is connected … with the ominous force of nature from which it pledges protection. It is produced against the background of the very clouds that had brought destruction to the earth. But it is produced upon these by the rays of the sun which in the symbolism of Scripture represent the divine grace” (67).