Charles H. Spurgeon on Psalms 106:30

Then stood up Phinehas, and executed judgment: and so the plague was stayed. God has his champions left in the worst times, and they will stand up when the time comes for them to come forth to battle. This righteous indignation moved him to a quick execution of two open offenders. His honest spirit could not endure that lewdness should be publicly practised at a time when a fast had been proclaimed. Such daring defiance of God and of all law he could not brook, and so with his sharp javelin he transfixed the two guilty ones in the very act. It was a holy passion which inflamed him, and no enmity to either of the persons whom he slew. The circumstances were so remarkable and the sin so flagrant that it would have involved great sin in a public man to have stood still and seen God thus defied, and Israel thus polluted. Phinehas was not of this mind, he was no trimmer, or palliator of sin, his heart was sound in God's statutes, and his whole nature was ablaze with zeal for God's glory, and therefore, though a priest, and therefore not obliged to be an executioner, he undertook the unwelcome task, and though both transgressors were of princely stock he had no respect of persons, but dealt justice upon them as if they had been the lowest of the people. This brave and decided deed was so acceptable to God as a proof that there were some sincere souls in Israel that the deadly visitation went no further. Two deaths had sufficed to save the lives of the multitude.