In a moment of dramatic crisis, the leadership of the Israelites stands paralyzed. A deadly plague is tearing through the camp, accompanied by a brazen public desecration of God's honor. Amidst the weeping and indecision, a single individual alters the course of events, stepping away from his traditional life of peace to take up arms and halt the disaster.
The catalyst for this sudden action prompts different interpretations. The primary approach among commentators is that witnessing the public sin triggered his memory of a specific law. This law states that if a man engages in public intimacy with a foreign woman, zealots acting for God's honor are permitted to strike him down. Alternatively, he may have seen a destroying angel ravaging the camp with the plague, realizing there was absolutely no time to delay [תורה תמימה]. A third perspective suggests he simply looked around, saw that no one else was stepping forward to protest the public disgrace, and decided he had to act himself [חזקוני, תורה תמימה].
The law of the zealot is highly unusual and is not carried out as a standard court sentence. In fact, if a person approaches the court to ask permission to execute the sinner, the judges must instruct him not to do it. The action is only valid if it erupts from a deep, spontaneous, and pure drive to defend God's honor at the exact moment the sin occurs [שפתי חכמים, מזרחי, ברכת אשר]. Because of this strict requirement, when Phinehas reminded Moses of this law, Moses could not explicitly command him to carry it out. Instead, Moses hinted that Phinehas must take the initiative himself, suggesting that the one who recalled the teaching should be the one to execute it [רש״י, רבנו בחיי, רא״ש].
His lineage as the grandson of Aaron the priest heavily underscores the magnitude of his action. As a scholar and a priest, he was a man of the spirit, entirely unaccustomed to warfare and bloodshed. Yet, he departed from his peaceful vocation and risked his life against the powerful tribe of Simeon to turn away God's anger [תולדות יצחק, צרור המור, רבנו בחיי]. At the time, he was sitting alongside Moses and the judges in the courtyard of the Tent of Meeting [אבן עזרא, רש ר הירש, ביאור שטיינזלץ]. While the rest of the leadership either wept or debated the proper legal response, Phinehas stood up from among them and took decisive action [רא״ש].
He armed himself with a spear, a weapon meant for throwing or stabbing [רש ר הירש]. However, he knew he could not march openly with a drawn weapon through the hostile crowd of Simeonites guarding the sinner. Relying on a clever tactic, he removed the iron spearhead and concealed it within his garments, leaning on the wooden shaft as if it were a simple walking stick. Only upon entering the tent did he reattach the blade. This specific detail later served as the basis for the legal tradition that one should not enter a study hall with an exposed weapon [רא״ש, תורה תמימה, שפתי כהן].
As a direct result of his courageous physical intervention, the priests of all future generations were granted a specific portion from slaughtered animals. They receive the foreleg, a permanent gift serving as a lasting tribute to the arm of Phinehas that firmly grasped the spear [רבנו בחיי, תורה תמימה].