Numbers 25:6

"And, behold, one of the children of Israel came and brought unto his brethren a Midianitish woman in the sight of Moses, and in the sight of all the congregation of the children of Israel, while they were weeping at the door of the tent of meeting. And when Phinehas, the son of Eleazar, the son of Aaron the priest, saw it, he rose up from the midst of the congregation, and took a spear in his hand; and he went after the man of Israel into the pavilion, and thrust both of them through, the man of Israel, and the woman through her body. So the plague was stayed from the children of Israel. And those that died by the plague Were twenty and four thousand. This very brief account centers around the daring execution of Zimri by Phinehas; but the implications of it are extensive. Zimri's importance and the rank of Cozbi are not mentioned till the last of the chapter. The most astounding thing here is that God honored this brutal execution by halting the plague that had already begun raging among the people. More on this later. It is evident that the words "in the sight of Moses" and "in the sight of all the congregation" indicate a frontal challenge to Mosaic authority and an open invitation for all Israel to follow Zimri."

From this instance, and from the example of Samuel's slaying of Agag, the Jews formulated what they called the "jus zelotarum," by which, any person seeing another in the very act of violating divine law might take vengeance into his own hand and slay the offender. God authorized no such thing. It was under this corrupt law (so-called) that the Jews stoned the Christian martyr Stephen to death, and under which, more than once, they tried to stone the Christ himself. The blind error of the Jews on this is that they failed to see why God commended Phinehas. It certainly was not for his taking justice into his own hands. It was his zeal that God commended. The next paragraph deals with God's commendation of Phinehas.