I have made you a sign for the house of Israel. In what must have appeared as a drama to the people, the Lord resorted to the use of “visual aids” to open the eyes of the rebellious Israelites to the fate that was awaiting them. God’s plea to them to change their ways in order to return to the path of righteousness had fallen on deaf ears. The people had brought this upon themselves, and it was only fair that they pay the price. And the price was not a cheap one. The Lord was going to “allow” Israel to be covered in shame by surrendering them into captivity (cf. Psalm 78:61). To show them the gravity of their disobedience, the Lord was going to let their capture to take place in broad daylight, that is, in their watch. They would be driven out of their land and taken into a foreign land, the worst punishment imaginable. 
The Lord commissioned Ezekiel to dramatize Israel’s exile to let them know that the Lord, in his anger, had “allowed” this to happen. The Lord had not forgotten them. Rather, it was the people who had forgotten about the Lord. Because the people turned their backs on the Lord, the Lord rejected and abandoned them. The Lord was going to allow the capture to take place while the people were “awake” because he wanted to show them that he had rejected them.