2 Kings 17:13
Yet the LORD testified against Israel, and against Judah, by all the prophets, and by all the seers, saying, Turn ye from your evil ways, and keep my commandments and my statutes, according to all the law which I commanded your fathers, and which I sent to you by my servants the prophets.
The Lord testified against both Israel and Judah by every prophet and every seer, repeatedly calling them to turn from their evil ways and to keep His commandments and His statutes according to all the law He had commanded their fathers and sent to them by His servants the prophets. Those warnings stood as a testimony against their wrongdoing. The law to which the call summoned them is binding in its claims, eternal and unchangeable.
The warning was given before Assyria captured Samaria and scattered the shattered remnant of the ten tribes among the nations early in Hezekiah's reign. Assyria's success in that conquest led many to question the power of the God of the Hebrews. Israel's later apostasy and downfall show the consequence of rejecting God's ways for human and heathen practices. Rejecting God's ways for human ways began Israel's downfall, which continued until the people became prey to the nations whose practices they had chosen to follow.
They refused the call, and after long patience their rebellion led to judgment, defeat by enemies, and captivity. Their rejection of His commands brought the judgment described in the surrounding account.