It states (6:13-14) בא בשר כל קץ ,לנח אלקים ויאמר גופר עצי תיבת לך עשה ...לפני, "Hashem said to Noach, 'The end of all flesh has come before Me.... Make for yourself an Ark of gopher wood..."
Rashi writes, "Hashem has many ways to save Noach. Why did Hashem have Noach toil to build the teivah? It was so that the people of the generation of the mabul should see him building it for 120 years, and they would ask him, 'Why are you building this structure?' He would tell them that Hakadosh Baruch Hu is about to bring a mabul to the world. Perhaps they will do teshuvah." We can learn from this how patient and how welcoming Hashem is to the teshuvah of mankind. The generation is notoriously known as המבול דור, the wicked generation of the flood. The people of this time were רשעים גמורים, total resha'im, as it states (6:12) השחית כי הארץ על דרכו בשר כל, "For all flesh had corrupted its way upon the earth". (See Rashi on this pasuk, and the Zohar, vol.1, 62a, for a description and severity of their aveiros). Nevertheless, Hashem didn't want to destroy them. Hashem had Noach build the teivah for 120 years, hoping that people would do teshuvah!
It states (7:12) הארץ על הגשם ויהי, "The rain was upon the earth," and Rashi notes that in this pasuk the Torah calls the rain גשם, and not מבול. This is because "If they do teshuvah, it would be ברכה גשמי, rain of a blessing. But if they don't do teshuvah, the rain would become rain of a mabul." This pasuk also shows us Hashem's patience with mankind. They had many severe aveiros, and they ignored Noach's warning for 120 years! Nevertheless, until the final moment, the opportunity to do teshuvah was still open for them. If they had done teshuvah before the flood began, their teshuvah would have been accepted. Not only that, but the waters of the flood would be blessed rain for them. The mabul would instead become ברכה גשמי, rain of blessing.
When we think about these matters, we are certain that Hashem desires the teshuvah of Bnei Yisrael. Hashem desires even the teshuvah of resha'im, so Hashem definitely desires the teshuvah of Bnei Yisrael. Their teshuvah will be accepted with desire before Hashem. (See Divrei Chaim, beginning of our parashah).
We say in the brachah of אור יוצר in Shacharis of Shabbos דלתות יום בכל הפותח ל"הא מזרח שערי, "Hashem Who opens the doors of the eastern gate, each day". Birkas Avraham taught that the roshei teivos of מזרח שערי דלתות spell ד"שמ, destruction, which means the phrase refers to a person who fell to the very lowest levels. Even for him, דלתות ...הפותח, Hashem opens the gates of teshuvah and enables him to change his ways and to come close to Hashem.
Reb Moshe Wolfson zt'l teaches: As it is known, everything that happens in the world, the decree for was established on Rosh Hashanah and Yom Kippur. On those days of judgment, everything that will occur that year is determined. Nevertheless, we see in this parashah that the decree can always be mitigated and turned around. The rain began on the 17th of Cheshvan, as it states (7:11-12) לחדש יום עשר בשבעה השני בחדש נפתחו השמים וארבת רבה תהום מעינות כל נבקעו הזה ביום הארץ על הגשם ויהי, "In the second month, on the seventeenth day of the month, on that day, all the foundations of the great deep burst forth; and the windows of heaven were opened, and the rain was upon the earth..." Rashi writes that, according to Reb Eliezer, השני חדש, the second month, refers to Cheshvan. According to Reb Eliezer, the mabul began on the 17th of Cheshvan. The Torah calls the flood water גשם, because if they would do teshuvah, the rain would become rain of a blessing (as we wrote above from Rashi). Reb Moshe Wolfson zt'l says that this teaches us that one can do teshuvah, and the verdict can change, even after it was established. We know and believe that the decree of the flood was signed and decided on Rosh Hashanah and Yom Kippur, but it could be changed in Cheshvan!
We read this parasha at the beginning of the year to teach us that regardless of what was decreed, it can be changed for the better.
It states (Bereishis 4:16) 'ה מלפני קין ויצא, and the Midrash (Bereishis Rabba 22:13) states, "Adam HaRishon met Kayin and asked, 'What happened in your judgment?' Kayin replied,
