וּבֶן־שְׁמֹנַ֣ת יָמִ֗ים יִמּ֥וֹל לָכֶ֛ם כָּל־זָכָ֖ר לְדֹרֹתֵיכֶ֑ם יְלִ֣יד בָּ֔יִת וּמִקְנַת־כֶּ֙סֶף֙ מִכֹּ֣ל בֶּן־נֵכָ֔ר אֲשֶׁ֛ר לֹ֥א מִֽזַּרְעֲךָ֖ הֽוּא׃
대대로 남자는 집에서 난 자나 혹 너희 자손이 아니요 이방 사람에게서 돈으로 산 자를 무론하고 난 지 팔 일 만에 할례를 받을 것이라
Rashi
יליד בית HE THAT IS BORN IN THE HOUSE — one to whom a handmaid gave birth in the house.
Radak
ובן שמונת ימים ימול, he is to be circumcised when 8 days old; a passive mode of the root מול. Accordingly, we must understand that the primary duty of performing the circumcision is that of the baby's father.
Rav Hirsch
(12-13) Wir haben im 4. und 5. Jahrgang des Jeschurun eine ausführliche Entwicklung der Milainstitution und ihrer Bedeutung versucht, und verweisen hierauf insbesondere noch hinsichtlich der Bestimmung, die Beschneidung am achten Tage, — (in besonderen Fällen auch sofort am ersten) — vorzunehmen.
Rashi
מקנת כסף HE THAT IS BOUGHT WITH THY MONEY — one whom a person bought after his birth.