According to John Currid in his commentary on Genesis concerning the flood, the number 40 in Hebrew is significant:
The rain will last for forty days and forty nights. The Hebrew number ‘forty’ is symbolic of a period of testing and trial. Israel, for example, is in the wilderness for four years of temptation. Goliath taunts Israel for forty days before his battle with David (1 Sam. 17:16). Jesus is tempted for forty days in the wilderness (Luke 4:2). So Noah and his family are about to undergo a great period of testing.
Currid also points out God’s absolute sovereignty in bringing the flood. This is interesting in light of a recent news of a liberal Baptist professor claiming that God isn’t actually sovereign. Yet, the bible disagrees.
Here is what Currid writes:
On the day God will ‘send rain’ to ‘exterminate’ life on earth (see 6:7; 7:23). The first of these verbs is a participle in the Hiphil pattern, indicating that God is the one who is bringing the rain. It is a great statement of sovereignty in which nature is at God’s beck and call.
Just some observations: first, God is sovereign over all of creation, including mankind. He can do with all of us as He pleases. It does not matter if mankind ignores God and suppresses the truth in unrighteousness, God still remains the judge over creation and will one day judge all of Creation again, including those who refuse to believe.
Secondly, He is gracious in giving us the account of the flood, showing His right and intent to judge again. In other words, it is God’s way of reminding us of our need for a Savior.
Third, He is merciful in giving us a way out of the judgment. Whereas Noah was saved through the ark, the greater Ark is Christ. He is the One who truly delivers us from God’s righteous wrath.