This verse comes from the story of Shadrach, Meshach, and Abednego in the Book of Daniel (though this specific wording appears in the Apocryphal additions). It describes the intensity and urgency with which the servants of King Nebuchadnezzar were stoking the furnace before throwing the three young men into it. Let's break it down:

"And the king's servants, that put them in...": This establishes who is performing the action: the king's designated servants tasked with carrying out the punishment.

"ceased not to make the furnace hot...": This emphasizes the continuous and relentless effort to increase the heat of the furnace. It was already extremely hot, but they were determined to make it even hotter.

"with naphtha, pitch, tow, and small wood": This lists the materials used to fuel the fire:

Naphtha: A highly flammable liquid, similar to gasoline or kerosene.
Pitch: A sticky, tar-like substance derived from petroleum or wood, also highly flammable.
Tow: Short, broken fibers of flax, hemp, or other materials, used for kindling. Tow burns quickly and intensely.
Small wood: Kindling, easily ignitable pieces of wood.

The combination of these materials indicates a deliberate and extreme effort to create an inferno. The servants were going above and beyond to ensure the furnace was as scorching as possible, which underscores the King's anger and determination to punish Shadrach, Meshach, and Abednego for refusing to worship his idol.

In essence, the verse highlights:

The King's ruthlessness: He wanted to make a brutal example of the young men.
The intensity of the test of faith: The three men were facing what seemed like certain death in a horrific manner.
The miraculous nature of their survival (which comes later in the story): If the furnace was so incredibly hot, their survival would be even more extraordinary. The hotter the fire, the more miraculous their rescue.

The verse serves to set the stage for the dramatic and miraculous deliverance of Shadrach, Meshach, and Abednego.