Tafsiran Keluaran 9:8: Rashi, Chizkuni, Rashbam & Sforno

מלא חפניכם HANDFULS (more lit., as much as will fill your fists), old French joincheiz; Engl, double-handfuls.

מלא חפניכם, “your handfuls,” this would not be enough soot to bring the plague on the entire land of Egypt; this is why the Torah does not attribute this plague as resulting from the fire that the soot was taken from. G-d did not want to change natural law at this point, and that is why He commanded Moses and Aaron to perform a symbolic act.

פיח, ash, dust particles remaining at the bottom of the furnace light enough to be carried by the wind.

פיח הכבשן SOOT OF THE FURNACE — the word פיח denotes a thing which is blown away (נפוח) from coals that have become extinguished after being burnt in a furnace; in old French oulvis.