HaSh-m had already given the people 120 years' warning. Why the additional seven days?
Rashi: These were the seven days of mourning of Mesushelach ha'Tzadik; HaSh-m postponed the Flood for another seven days in deference to him.
Targum Yonasan: HaSh-m gave them a last chance to do Teshuvah - a final warning 1 closer to the occasion. 2
Hadar Zekenim #1: They were seven days to mourn the loss of the world. 3
Hadar Zekenim #2: During these days, HaSh-m gave them a taste of the world to come - to show what they would lose, or could yet attain if they would repent. Refer to 7:4:1.3:2.
Hadar Zekenim: During those seven days, the sun rose in the west and set in the east. Refer to 7:4:1.3:1.
See Rashi here, and Rashi to Shemos 19:24.
Similarly, HaSh-m commanded Aharon and his sons not to leave the entrance of the Ohel Mo'ed for seven days (Vayikra 8: 33-35). These days would serve as mourning over Nadav and Avihu - who would perish only afterwards (Vayikra 10: 1-2).
What is the significance of the forty days during which HaSh-m blotted out the world?
Rashi It corresponds to the forty days in which a baby is formed, and to the trouble to which they put Ha'Kadosh-Baruch-Hu to form the Mamzerim that they conceived.
QUESTIONS ON RASHI
Rashi writes: "'In another seven days' - [This was] an additional time period, after the 120 years had concluded." What did Rashi find difficult in the verse?
Gur Aryeh: The verse could have stated, "In seven days," without the word "another." Rather, these seven days were in addition to the 120 years.
Rashi writes: "'In another seven days' - these are the days of mourning for the righteous Mesushelach." What is the source for this in the verse?
Gur Aryeh: Why would HaSh-m need to warn Noach seven days in advance? It must be that the seven days were for another reason, namely, the honor of Mesushelach. HaSh-m informed Noach of this, so that he should not ask why the Mabul had not yet arrived, since the deadline of 120 years had already arrived (Refer to 7:4:0.1).
Rashi writes: "These are the days of mourning for the righteous Mesushelach." Why did HaSh-m delay the Mabul for this reason?
Maharal #1 (Chidushei Agados, Vol. 3, p. 257): Eulogy for the righteous is considered the honor of the departed (as opposed to the honor of the assembled), therefore, HaSh-m did not bring the Mabul and interrupt the seven days of mourning.
Maharal #2 (ibid.): The pain of the passing of the righteous was sufficient for the time being; HaSh-m does not bring one tragedy on top of another.
Rashi writes: "These are the days of mourning for the righteous Mesushelach." What took place during these seven days?
Maharal #1 (Chidushei Agados, Vol. 3, p. 257): Chazal teach that during these seven days, the sun rose in the west and set in the east; the destruction of the world followed the reverse order of its creation.
Maharal #2 (ibid.): Chazal teach that during these seven days, HaSh-m gave the people a taste of Olam ha'Ba. In contrast to other generations that have been punished, the generation of the Mabul was wiped out eternally, therefore, HaSh-m gave them their Olam ha'Ba in this world. 1
He adds that because the world was created in seven days, their taste of Olam ha'Ba lasted for seven days.
