Daniel 3:20 (ESV)

20 And he ordered some of the mighty men of his army to bind Shadrach, Meshach, and Abednego, and to cast them into the burning fiery furnace.

Nebuchadnezzar sends for the strongest soldiers to make sure that Shadrach, Meshach and Abednego cannot escape. Everything has to be done to ensure that these rebels are publicly punished. It is imperative that no one breaks Nebuchadnezzar’s ideal of unity with impunity and these young men are a danger to the unity of the kingdom. If Nebuchadnezzar does not set an example now, the representatives of all nations might start thinking that they do not have to take this king all that seriously. This will lead to rebellion and disobedience to the mighty Nebuchadnezzar.