וְעָשִׂ֣יתָ קַרְנֹתָ֗יו עַ֚ל אַרְבַּ֣ע פִּנֹּתָ֔יו מִמֶּ֖נּוּ תִּהְיֶ֣יןָ קַרְנֹתָ֑יו וְצִפִּיתָ֥ אֹת֖וֹ נְחֹֽשֶׁת׃
Tu sculpteras ses cornes aux quatre angles, de sorte qu’elle fassent corps avec lui et tu le revêtiras de cuivre.
Rashi on Exodus
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 on Exodus
קרנותיו, a feature of all altars, as were the shovels and the basins for the blood as receptacles.
Rashbam on Exodus
ממנו תהיין קרנותיו, integral parts of the structure, not something superimposed.