Daniel 3:17 (ESV)

17 If this be so, our God whom we serve is able to deliver us from the burning fiery furnace, and he will deliver us out of your hand, O king.

The three friends confess here that the Lord, if he wills, can save them even now in that fiercely burning furnace. He is able to rescue them from this furnace.

Now the king should not be mistaken, even if the Lord allows them to die in it, this is no proof that Nebuchadnezzar and his gods are stronger than the Lord. The Lord is the only living God! The king has to be reminded that this is the reason why these three will not worship other gods and this great image. If the three friends die in the furnace, they will go to be with the Lord and live with him in heaven. They will stand there rejoicing before his throne. The Lord Jesus also makes it clear that if a believer dies for his faith this does not mean that God is defeated. We read this great encouragement in Matthew 10:28–32, “And do not fear those who kill the body but cannot kill the soul. Rather fear him who can destroy both soul and body in hell. Are not two sparrows sold for a penny? And not one of them will fall to the ground apart from your Father. But even the hairs of your head are all numbered. Fear not, therefore; you are of more value than many sparrows. So everyone who acknowledges me before men, I also will acknowledge before my Father who is in heaven.”