Rashi on Genesis 7:4/רש"י על בראשית ז׳:ד׳

1כי לימים עוד שבעה FOR YET SEVEN DAYS — These are the seven days of mourning for the righteous man Methuselah for whose honour the Holy One, blessed be He, had regard, and therefore postponed punishment. Go and calculate the years of Methuselah and you will find that they came to an end (i. e. he died) in the six hundredth year of Noah’s life (which coincided with the date of the Flood) (Sanhedrin 108b).

2כי לימים עוד FOR YET [SEVEN] DAYS — What is meant by עוד "yet", "more"? A further period of time: this period (seven days) additional to the 120 years of respite that was promised (Sanhedrin 108b).

3ארבעים יום FORTY DAYS — corresponding to the period of a child’s formation, for by their sinning they had troubled their Creator to form embryos of illegitimate children (Genesis Rabbah 32:5).