Rashi on Genesis 8:13/רש"י על בראשית ח׳:י״ג

1בראשׂון IN THE FIRST MONTH — According to R. Eliezer this would be Tishri, and according to R. Joshua Nisan (Rosh Hashanah 11b).

2חרבו [THE WATERS] DRIED UP — It (the earth) had become like clay, for now its surface had become somewhat hardened.