Komentaryong Sumisipi para sa Isaias 48:4

"And you shall make the altar of acacia wood." In the Midrash Tanchuma (10), it concludes: "They committed folly [שטות] and angered Me with the [golden] calf, so let the acacia [שטים] wood come and atone for their folly." This is because a spirit of folly [שטות] enters every sinner (Sotah 3a). For this reason, Solomon refers to the wicked as fools, and therefore it says regarding the altar, "hollow with boards shall you make it," because anyone who is without knowledge and understanding is called a hollow man [נבוב], as it is said (Job 11:12), Let the hollow man gain understanding - Rashi explains there that anyone who is empty and hollow without knowledge and understanding needs to acquire a heart to return in repentance.
And its height shall be three cubits - like the height of an average person. And five cubits in length and five cubits in width - making ten, corresponding to the ten things that come from a father and mother: flesh, blood, sinews, etc., as enumerated in Tractate Niddah (31a). And through these comes all sin and iniquity, and this is [also indicated by] the half-shekel of ten gerahs.
And you shall make its horns - to atone for the sinner who is compared to a ram with horns that gores upward, as it is written (Psalms 75:5-6), And to the wicked, "Do not lift up the horn; do not lift up your horn on high", as explained above in Parshat Vayera in the verse And behold, a ram caught afterwards.
And you shall overlay it with copper - Rashi explains, to atone for brazenness, as it is said [with reference to brazenness] (Isaiah 48:4), and your forehead is copper. This agrees with our explanation, since every horn is on the forehead.

A Midrashic approach (based on Tanchuma Terumah 11): when the Torah wrote: “you shall make an altar of shittim wood and overlay it with copper,” what was this altar to atone for? For the effrontery characterized by a “copper-hard forehead.” We have a verse in Isaiah 48,4 where this simile is used for stiff-necked behavior. The prophet writes: ”because I know how stubborn you are; your neck is like an iron sinew, and your forehead bronze.” It is also worth noting that the letters in the word מזבח, “altar,” may be understood as an acrostic of the first letters in the words מחילה, זכות, ברכה, חיים respectively. The word שטים may also be understood as an acrostic of the first letters of the words שלום, טובה, ישועה, מחילה respectively. The measurements of five by five cubits for the length and width of the altar corresponded to the two Tablets of the covenant on each of which five of G’d’s directives had been engraved. The height described by the Torah, i.e. three cubits, is an allusion to the three redeemers of the Jewish people, Moses, Aaron, and Miriam. Thus far the Midrash.

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).