Numbers 25:7

And when Phinehas, the son of Eleazar, the son of Aaron the
priest, saw it
Saw the man pass by in this impudent manner, and his whore with him; his spirit was stirred up, he was filled and fired with zeal for the glory of God, and with an holy indignation against the sin and sinner, and with a just concern for the honour of the righteous law of God; and, to prevent others from falling into the same sin, led by the public example of so great a personage, as it appears afterwards this man was:

he rose up from among the congregation;
who were weeping at the door of the tabernacle, or from the midst of the court of judicature, set for trying and judging such persons who were charged with idolatry; for he was not only the son of the high priest and his successor, but a ruler over the Korahites, and had, besides his priestly office, a civil authority, ( 1 Chronicles 9:20 )

and took a javelin in his hand;
a spear or pike; the Jews say ^F25 he snatched it out of the hand of Moses; and, according to Josephus ^F26, it was a sword; but the word rather signifies an hand pike; this being ready at hand, he took it up and pursued the criminal.