The Kingdom of Israel, represented by the tribe of Ephraim, sank into a deep moral decay. Despite experiencing God's past kindness and knowing the truth, the people chose a path of idolatry, bloodshed, and blatant disrespect, making severe punishment unavoidable. The primary approach among commentators is that the nation deeply provoked God through their betrayal and their scorning of His prophets [רש״י, אבן עזרא, רד״ק, מצודת דוד, שטיינזלץ]. Alternatively, this intense anger was directed at the prophets themselves, as the people of Ephraim constantly mocked and ridiculed those who tried to correct them [מלבי״ם].
The nature of this provocation is widely understood to be exceptionally bitter and severe [מצודת ציון, רד״ק, מלבי״ם, שטיינזלץ]. However, others view this severity in terms of its public brazenness. Rather than hiding their actions, the people sinned openly [אבן עזרא], constructing prominent idolatrous altars that stood out in the landscape like obvious road markers [רד״ק].
A central element of their guilt involves the shedding of blood. Most commentators take this literally, pointing to the innocent lives that Ephraim destroyed [אבן עזרא, רד״ק, מצודת דוד, שטיינזלץ]. A different perspective views this as spiritual murder. By leading the Israelites into idolatry, Ephraim committed a crime considered even more destructive than physical killing [רש״י]. The consequences of this bloodshed are inescapable. The spilled blood is seen as spreading over the guilty to demand vengeance [מצודת ציון, מצודת דוד, רד״ק], or it signifies that God will firmly place the full weight of responsibility upon them, ensuring they face justice for their actions [רש״י, מלבי״ם, שטיינזלץ].
Ultimately, the disgrace the people caused will be returned to them by their master. Most identify this master as God. Because Ephraim disgraced God by trading Him for golden calves, God—who remains their ruler regardless of their rebellion—will pay them back with absolute disgrace [מצודת דוד, רד״ק, שטיינזלץ]. One tradition traces this specific disgrace back to Jeroboam, a leader from Ephraim, who once publicly shamed King Solomon for his flaws, only to later commit far worse sins himself [רש״י].
A completely different approach suggests the master refers to a human king whom the people had assassinated. According to this view, the Israelites murdered their leaders under the pretense of rooting out idolatry, yet continued to worship idols themselves. In a striking poetic image, the murdered king rises from his grave to throw his unjustly spilled blood back at his assassins, returning the very insults they shouted at him during his murder [מלבי״ם].