Do not be deceived—you may not be described with what you know
In The Name of Allaah, The Most Merciful, The Bestower of Mercy
How many people know about love of Allaah, its rulings and all the affairs it necessitates; but his heart is deprived of it?! And how many a slave knows and bears witness to the pre-decree of Allaah and the excellence of sufficing oneself with Him; but when that which has been decreed takes place in opposition to what he likes, you see him anxious—having neither tranquility (and) certainty nor repose?! And only the one whose heart has acquired knowledge and awareness of Allaah in truth is tranquil about Allaah being sufficient for him, whilst submitting to His judgments, whatever the state of affairs may turn out to be. And how many people know the rulings of trade and its details; but at the time of dealing, buying and selling, he does not deal in a beautiful manner with others?! This is the same in many affairs with regards to this pattern of behaviour.
Therefore, do not be deceived when you know something that you will be attributed to it, and that is why it is legislated for the slave to ask Allaah for beneficial knowledge, and that is knowledge that produces actions (as its fruits). And Allaah knows best.
[Source: By Imaam Abdur-Rahmaan As-Sadi (rahimahullaah) paraphrased and abridged http://www.sahab.net/forums/index.php?showtopic=136031 ]