A prophet's personal tragedy sometimes becomes a living symbol of a national catastrophe. The unusual way Ezekiel behaves during his own mourning is meant to mirror exactly how the entire nation will react when their homeland is destroyed. In delivering this message, Ezekiel refers to himself in the third person rather than the first person. This reflects that he is speaking directly in God's name, quoting His exact words to the people [רד"ק].
God declares that the prophet will serve as a clear sign and a living example for the nation. The people are destined to act exactly as Ezekiel did following the death of his wife, meaning they will be so overwhelmed that they will not observe the standard, traditional customs of mourning [מצודת דוד, מצודת ציון, ביאור שטיינזלץ, אברבנאל].
When the disaster finally strikes—whether that is the actual moment the destruction falls upon Jerusalem and the Temple, or the moment the devastating news reaches the exiles—it will completely shatter the false hopes of the people. Until that point, they mistakenly believed that Jerusalem would be spared simply because God's Temple stood within its walls [אברבנאל]. Ultimately, the fulfillment of this harsh prophecy will lead to a profound realization. The nation will finally understand that God carries out His words completely, recognizing His faithfulness to exact justice and repay them for their actions [מצודת דוד, ביאור שטיינזלץ].