Despite seeing all that had happened in the north, Judah did not return to the Lord with her whole heart, but in pretense.
The Hebrew word for pretense
is seqer and it means deception, a lie.
1 Josiah did bring about religious reforms in Judah, and he restored Temple worship. But these changes were all on the surface. In Deuteronomy the essence of the covenant is for Israel to search after [the LORD] with all your heart and soul
(Deuteronomy 4:29) and to love the LORD your God with all your heart and with all your soul and with all your might
(Deuteronomy 6:5). The religious reforms Josiah put in place had not changed the people of Judah. It was all empty religion with no change of heart.
The implication of course is that Judah will face the same consequences as Israel did in the north. But there is still no direct mention of judgment. When Jeremiah passes these words that the Lord has spoken to him on to Judah the aim, in part at least, is still to call Judah to repentance before judgment comes.2
10 Yet for all this her treacherous sister Judah did not return to me with her whole heart, but in pretense, declares the LORD.”