Shaykh Uthaymeen said:

Verily, we all know that the intent of knowledge is action. Because knowledge is a means and action is the fruits. And if a person does not benefit with his knowledge, then an ignoramus is better than him. And many knowledge based issues are understood by most students, however they do not carry them out, whether it was in (issues of) worship, or dealings with the creation. And this there is no doubt is a deficiency; a deficiency, and a reason for deficiency, meaning deficiency in knowledge. For if a person was to act by his knowledge he benefits and his knowledge increases. So, whoever acts by that which he has learnt, then Allāh will forgive him for that which he did not know.