Men have such a good opinion of themselves, of their mental superiority and intellectual depth; they believe themselves so skilled in discerning the true from the false, the path of safety from those of error, that they should be forbidden as much as possible the perusal of philosophic writings.
Al-GhazaliWhen you have a bad suspicion about a Muslim in your heart, you should increase your consideration toward him and make dua for him. This way you will infuriate Satan and will be able to drive him away. Because of this, Satan will be reluctant to put evil thoughts into your heart, afraid that you would increase your consideration towards your brother and will make dua for him again.
Al-GhazaliO youth.......be assured that knowledge alone does not strengthen the hand......Though a man read a hundred thousand scientific questions and understood them or learned them, but did not work with them---They do not benefit him except by working.....Knowledge is the tree, and working is its fruit; and though you studied a hundred years and assembled a thousand books, you would not be prepared for the mercy of Allah the Exalted except by working.
Al-Ghazali