Why does it say "Libo Yatzuk Kmo Aven"?
'Rashi': Its heart is as hard and firm as a rock fixed strongly in a building's foundation.
Ibn Ezra: This is like "v'Yatzakta Lo" (pouring). Its heart is as strong as rock.
What is "v'Yatzuk k'Felach Tachtis"?
'Rashi': The expression is repeated. Its heart is fixed like the bottom millstone. The top stone rotates and grinds; the bottom stone does not move - it is fixed in its place. It is called Pelach - "va'Tashlech Ishah Achas Pelach Rechev Al Rosh Avimelech." The bottom stone is called Pelach Tachtis. Ibn Ezra - it is strong.
Malbim: In all living beings, the heart moves and presses. It heart does not move at all, like the bottom stone, and unlike the top stone.
