«اِلرَّحَى مَا تْدُورْ إِلَّا عَلَى قَلْبْ حَدِيدْ»

A grinding stone keeps turning only if the pin at its center, called its heart, is made of something unyielding, like iron. Here heart means that central pin, not emotion. All the motion at the rim depends on a hidden core sturdy enough to carry the load.

Applied to people, it says that weighty affairs are managed and carried through only when a strong, capable person stands at their center. The point is steadiness and competence, not hard-heartedness, ruthlessness or harshness toward others.

Fits talk about leadership or demanding work, such as arguing that a task needs a dependable person in charge, crediting someone whose steadiness keeps things running, or cautioning against giving heavy responsibility to someone weak.