It lurketh in wood and never consumeth it till it is ignited by others. That very fire, when brought out by friction, consumeth by its energy not only the wood in which it lurketh, but also an entire forest and many other things. Men of high lineage are just like fire in energy. Endued with forgiveness, they betray no outward symptoms of wrath and are quiet like fire in wood. Thou, O king, with thy sons art possessed of the virtue of creepers, and the sons of Pandu are regarded as Sala trees.

In plain words: Fire hides inside wood and does no harm until someone sparks it. Once lit, it can burn the wood and a whole forest. Noble people are like that fire: they are forgiving and look calm, but they have great hidden power. Vidura compares the king and his sons to creepers and the Pandavas to tall Sala trees.