בַּיָּמִ֣ים הָהֵ֔ם חָלָ֥ה חִזְקִיָּ֖הוּ לָמ֑וּת וַיָּב֣וֹא אֵ֠לָיו יְשַׁעְיָ֨הוּ בֶן־אָמ֜וֹץ הַנָּבִ֗יא וַיֹּ֨אמֶר אֵלָ֜יו כֹּֽה־אָמַ֤ר יְהוָה֙ צַ֣ו לְבֵיתֶ֔ךָ כִּ֛י מֵ֥ת אַתָּ֖ה וְלֹ֥א תִֽחְיֶֽה׃
In those days was Hezekiah sick unto death. And Isaiah the prophet the son of Amoz came to him, and said unto him: ‘Thus saith the LORD: Set thy house in order; for thou shalt die, and not live.’
Akeidat Yitzchak
The meaning of our opening aggadah is as follows. If you refrain from contact with your wife during the seven days of the menstrual cycle, tum-ah, you will merit the blessing of the eighth day, i.e. circumcision, which symbolises ascendancy over the spirit of impurity, attainment of purity. Since "seven days" represent the "creation cycle," the number seven always reminds man both of his duties and of his limitations on this planet.