Knowledge without action is madness; action without knowledge cannot be.
العلم بلا عمل جنون، والعمل بغير علم لا يكون
Al-ilmu bilā amalin junūn, wa'l-amalu bi-ghayri ilmin lā yakūn
Al-Ghazali, Ayyuha'l-Walad.
Knowing is one thing.
Living what you know is another.
Al-Ghazali writes to his student.
He counts knowledge that is not lived as madness.
For to know and not to do
is the mind's betrayal of itself.
Action without knowledge cannot be at all.
One who does not know the way, even if he walks, does not arrive.
The saying is not from the Ihya, but from Ayyuha'l-Walad.