A harsh rebuke is directed at the nation of Edom for their conduct during the destruction of the First Temple and the collapse of the Kingdom of Judah. Because Judah had ruled over Edom for many years, witnessing Judah's defeat artificially inflated the Edomites' self-image, leading them to gloat over the tragedy [ביאור שטיינזלץ]. The prophet details a step-by-step escalation of moral failures, highlighting Edom's growing cruelty and their ultimate betrayal of brotherhood [מלבי״ם, מצודת דוד].
The moral decline begins with the simple act of looking. Most commentators agree that the Edomites should never have stood by to watch their brother's downfall. Even if they lacked the power to help, they should have remained in their homes rather than gazing upon Judah's shame with contempt, satisfaction, or mere curiosity [מצודת דוד, ביאור שטיינזלץ].
This period of tragedy is understood in several ways to capture the depth of the disaster. The primary approach among commentators views it as a time of profound alienation. It was the moment the people of Judah were driven from their land and turned into strangers [רד״ק, מצודת דוד, צאינה וראינה], a time when the entire world turned its back on them [ביאור שטיינזלץ]. It was also the exact moment Edom chose to treat Judah as foreigners, completely breaking their brotherly bond [מלבי״ם]. Alternatively, this time represents the specific moment Judah was handed over to the Babylonian enemy [רש״י, רד״ק]. Another perspective suggests it was a day of strange and heavy disaster, an event unlike anything Judah had ever experienced before [אבן עזרא].
From merely watching, the cruelty escalates to a deeper, internal offense. It was not enough for the Edomites to stand and observe; they actively felt joy in their hearts over the destruction and loss of their brothers [מצודת דוד, מלבי״ם].
The final and most severe stage of this moral failure is the outward expression of that inner malice. The Edomites spoke with arrogance, laughter, mockery, and contempt [רד״ק, צאינה וראינה, מצודת דוד]. Rather than keeping their cruel satisfaction hidden, they openly encouraged the destruction and publicly mocked the fall of Israel [מלבי״ם].