וְעָשִׂ֤יתָ בַדִּים֙ לַמִּזְבֵּ֔חַ בַּדֵּ֖י עֲצֵ֣י שִׁטִּ֑ים וְצִפִּיתָ֥ אֹתָ֖ם נְחֹֽשֶׁת׃
Gagawa ka ng mga pasanan para sa altar, mga pasanang yari sa kahoy na akasya, at babalutin mo ang mga ito ng tanso.
Mekhilta DeRabbi Yishmael
Similarly, (Exodus 20:22) "And im ("when") an altar of stones you make unto Me." It is mandatory. You say it is mandatory, but perhaps it is optional? (Devarim 27:6) "Of whole stones shall you build the altar of your G–d" indicates that it is mandatory and not optional.