In the sugya: The word “etzim” is expanded by the Gemara to include any combustible material suitable for sustaining a fire, not only substantial logs.
Type of Learning
Ribbuy of any combustible for the fire — any wood-like fuel, including straw, may sustain the burning.
What Is Learned
The fire that consumes the chatas bull may be fed by straw or stubble as well as by ordinary wood. The ribbuy of “al etzim” removes any requirement that the fuel be of a particular grade or size; whatever will keep the fire burning is acceptable.