וְעָשִׂ֣יתָ קַרְנֹתָ֗יו עַ֚ל אַרְבַּ֣ע פִּנֹּתָ֔יו מִמֶּ֖נּוּ תִּהְיֶ֣יןָ קַרְנֹתָ֑יו וְצִפִּיתָ֥ אֹת֖וֹ נְחֹֽשֶׁת׃
און זאָלסט מאַכן זײַנע הערנער אױף זײַנע פֿיר װינקלען; פֿון אים גופֿא זאָלן זײַן זײַנע הערנער; און זאָלסט אים איבערציען מיט קופּער.
Rashi
ממנו תהיין קרנתיו ITS HORNS SHALL BE OF THE SAME — i. e. he shall not make them separately and afterwards attach them to it (to the altar).
Sforno
קרנותיו, a feature of all altars, as were the shovels and the basins for the blood as receptacles.
Rashbam
ממנו תהיין קרנותיו, integral parts of the structure, not something superimposed.
Rav Hirsch
צוטריטלעך נאָר פֿאַר פּרעמיום־מיטגלידערRashi
וצפית אתו נחשת AND THOU SHALT OVERLAY IT WITH COPPER — to atone for sins committed with effrontery (more lit., with impudence of forehead, the Hebrew expression for effrontery being, “having a copper forehead,”) as it is said, (Isaiah 48:4) “[Because I know that thou art obstinate] and that thy forehead is copper” (cf. our English expression “brazen-faced”) (Midrash Tanchuma, Terumah 11).