מלכים ב, פרק ט״ז, פסוק י״ב

Upon returning from Damascus, King Ahaz inspects a newly constructed altar and finds it greatly to his liking [ביאור שטיינזלץ]. This moment marks the peak of the king's wickedness, as his actions demonstrate a complete rejection of the worship of God and the established laws of the priesthood. The very existence of a second altar stands in direct opposition to the core principle of unity in worship. Furthermore, by allowing a non-priest to perform the sacred duties, he actively violates the covenant of the priesthood [מלבי״ם].

When it comes to the king's specific interaction with this new altar, there are a few ways to understand his exact level of involvement [מלבי״ם, רד״ק]. One perspective suggests that he took full control of the ritual, personally bringing and offering his sacrifices upon the altar [רד״ק, אברבנאל, מצודת דוד, ביאור שטיינזלץ]. Another view focuses on his physical movement toward the structure. In this understanding, he either walked right up to the altar to perform the sacrifices himself [רד״ק], or he simply stood close to it while others carried out the actual offerings [אברבנאל].