“even rising up early and sending them.” This is an idiom meaning to send again and again, and generally be eager to do it. The idea is that God rose up early and sent His prophets, and sent them over and over as the day progressed. The same idiom occurs in Jeremiah 7:13, 25; 26:5; 29:19; 32:33; 35:15. We have kept the idiom but inserted the meaning of the idiom by adding “again and again” in italics. But the people rose up early to do evil (Zeph. 3:7. Zephaniah and Jeremiah both prophesied during the reign of Josiah, king of Judah).
We can hear the frustration in God’s voice. He does not want anyone to be hurt or lose out on everlasting life, but people have to make their own choice. Meanwhile our loving God gives people chance after chance, sending prophet after prophet to bring them back to Him. He wants people to turn from their evil ways so He can repent and disaster can be averted (Jer. 26:3). But we know the end of the story. Judah did not listen, and so the Temple was burned down and the people were carried away captive to Babylon.