Rashi: Initially, Hashem told him "v'Ne'elamta v'Lo Sihyeh Lahem l'Ish Mochi'ach" (3:26) "b'Yom Kachti Mehem Es Ma'uzam; ? Yavo ha'Palit Elecha?; ba'Yom ha'Hu Yipasach Picha Es ha'Palit? v'Lo Se'alem Od" (24:25-27).

Malbim: Hashem told Yechezkel (3:26) to be silent; He will tell him the night before the Palit comes, and open his mouth from then and onwards. Yechezkel was not the designated Navi about the Churban, rather, Yirmeyah was, in Yerushalayim. It was still possible to avert the Churban via Teshuvah. Had Tzidkiyah heeded Yirmeyah and surrendered to Nebuchadnetzar, he would not have destroyed the city! In Galus, Yirmeyah commanded them to father children, for they will be there for 70 years. Initially Yechezkel was silent, for the possibility [to avert the Churban] depended on Yirmeyah's prophecy. After the Churban, Yirmeyah's mission was finished, and then Yechezkel prophesized to the nation. Until then, people believed the false Nevi'im who said that the Mikdash will not be destroyed.

Rashi: It is before he came to me in the morning.