عَلَى الذَّبْلِ جَيَّاشٍ كَأَنَّ اهْتِزَامَهُ
إِذَا جَاشَ فِيهِ حَمْيُهُ غَلْيُ مِرْجَلِ
“Though lean in build, he surges with vigor; when his heat rises, his intense movement resembles the boiling of a pot.”
ʿAlā al-dhabl refers to a lean or spare build, while jayyāsh suggests energy that wells up repeatedly. Bringing these together is significant: the animal is not corpulent, yet it is full of force and fire.
Ghalyu mirjal is the boiling of a cooking vessel. This is not a scientific measurement of the horse's temperature. It is a sensory comparison presenting concentrated energy through a familiar sight and sound of turbulence.