Why is it written "Se'i" and "Re'i", and we pronounce them Se'u" and "Re'u"?
Radak #1: The Kesiv corresponds to Keneses Yisrael (singular); the end of this and the next two verses is singular. The pronunciation corresponds to the individuals (plural).
Radak #2: He said "Se'u" and "Re'u" to the king and the Gevirah (his mother). The flock was theirs; they were the shepherds. It says "Lach" and "Tif'artech" (feminine) corresponding to the Kenisah (gathering) of great officers who were exiled with Yehoyachin, ha'Charash veha'Masger. The herd was also theirs; they are among the shepherds.
What should they see?
Radak: They should see the Bavliyim coming from the north to exile them.
Malbim (19-20): When Nebuchadnetzar went to face Pharaoh's army, Tzidkiyah thought that Nebuchadnetzar will not return to Yerushalayim. The Navi tells him to see that the ones approaching are Nebuchadnetzar's army from the north, and not Pharaoh's army from the south.
Why does it say "ha'Eder Nitan Lach"?
Radak: See the herd that was given to you, to be a shepherd over them, where are they now? You will not tend them any more.
Malbim: This is the remnant left after the exile of Yehoyakim; they were given to you to be king over them.
