שמות, פרק כ״ז, פסוק ב׳

The construction of the altar involves prominent architectural elements at its upper edges, carrying both structural and symbolic meaning. The design focuses specifically on the four corners of the structure [אבן עזרא]. At these corners are protrusions, conceptually borrowed from the horns of animals, a term used to describe anything jutting upward from the top of an object [הכתב והקבלה]. These elements are straight, square extensions [ביאור שטיינזלץ], taking the shape of a hollow cube measuring one cubit in length, width, and height [רלב״ג, הכתב והקבלה, ביאור יש״ר].

The instructions present these upward extensions as if they are already familiar. Some explain that this is because such elements were an integral and widely recognized feature of any standard altar [ספורנו, קאסוטו]. Alternatively, Moses had already seen the spiritual blueprint of the altar at Mount Sinai and recognized its general shape. Therefore, the instruction does not introduce the concept of these corners but rather teaches a specific technical detail that Moses could not have understood merely from a visual vision [העמק דבר].

This crucial detail dictates that the upper corners cannot be manufactured separately and attached to the altar later. Instead, they must form a single piece with the main body, acting as a direct continuation of the wooden beams that make up its sides [רש״י, רשב״ם, רלב״ג, קאסוטו]. Practically, the two outer walls of each corner must be a seamless extension of the altar walls themselves, creating a visual effect of the entire structure striving upward [רש ר הירש, ברכת אשר על התורה]. This requirement is absolute, and an altar lacking four upper extensions continuously integrated into its body is completely invalid for bringing sacrifices [רלב״ג].

Once the wooden frame is complete, the entire altar, including its sides and walls, is overlaid with copper [ביאור שטיינזלץ, קאסוטו]. This choice of material requires an explanation. Generally, the sanctuary follows the principle that poverty has no place in an environment of wealth, leading to the expectation that precious metals like silver or gold should be used. However, the choice of copper serves a deeply symbolic purpose. It is meant to atone for the sin of arrogance, as copper represents stubbornness and audacity in biblical tradition [רש״י, משכיל לדוד].