2 Kings 17:26
Wherefore they spake to the king of Assyria, saying, The nations which thou hast removed, and placed in the cities of Samaria, know not the manner of the God of the land: therefore he hath sent lions among them, and, behold, they slay them, because they know not the manner of the God of the land.
Israel had neglected God's statutes and sinned, and was overcome and conquered by an idolatrous nation, after which the king of Assyria removed foreign peoples and settled them in the cities of Samaria. Those newcomers did not know the manner of worship required by the God of the land. Because they did not know that manner and had adopted idolatrous worship, lions were sent among them, and with other disasters slew them, as God's judgment. They understood those troubles as God's punishment for apostasy and sought instruction in the true religion, so that their worship became more like that of the Jews.
Even after adopting the Jewish faith and customs and the Mosaic ritual, they did not wholly give up idol worship but mixed Judaism with heathenism, claiming to worship the true God while retaining images and reverence for graven images. That mixed population was afterward joined by those who had married idolaters and by those expelled from the congregation, including former leaders of God's work. They built a rival temple on Mount Gerizim and claimed to be God's people, producing the Samaritans' separation from Israel and lasting division and hostility with the Jews.