«اِلْجَدَارِ الْعَرِيضْ مَا يْعِبْش»

The image comes from building work. The part of a wall sunk into the ground stays out of sight, yet it decides whether everything above it holds. When that base is laid wide and firm, the structure resting on it stays straight, whole and free of defects.

More broadly, the saying fits anything whose soundness depends on strong underpinnings. It may also point to a person of good stock: someone whose roots are sound tends to offer those around them nothing but good, giving them no reason for reproach.

Suited to remarks about anything, whether a structure, an enterprise or an arrangement, that holds up well because its base was built solidly. It can also be said admiringly of someone from a good family whose conduct gives others no cause for complaint.