Rashi on Genesis 7:2/רש"י על בראשית ז׳:ב׳

1הטהורה CLEAN—It means those cattle which will in future be permitted to Israel as clean; we thus learn that Noah studied the Torah.

2שבעה שבעה SEVEN AND SEVEN — so many, in order that he might offer some of them as a sacrifice when leaving the Ark (Genesis Rabbah 34:9).