My dear son...
To advise others is an easy matter. The difficulty is accepting advice, since this is a bitter thing for those who follow their own inclinations and desires. They love the forbidden from the depth of their hearts. This is more applicable to seekers of knowledge and students of learning, those of them who are busy in the grace of spirits and the benefits of this world. They believe that mere abstract knowledge, without proper action, will rescue them. This is the belief of the philosophers. Praise and be glory to Allah, the Greatest of all. They do not know this much, that when they acquire knowledge, if they do not work according to it, the indictment against them is certain. The Messenger of Allah s.a.w said: "The person most severely punished on the Day of Judgment is the learned one who did not follow Allah's guidance and did not benefit from his knowledge." It has been narrated that someone saw al-Junayd (may Allah be pleased with his soul) after his death in a dream. Al-Junayd was asked: "What news do you have, Abul Qasim?"
He replied: "Perished are the speeches and vanished are the allusions; nothing benefited us except the prostrations which we made in the middle of the night."
Imam Abu Hamid al-Ghazali speaking in Third Counsel of Ayyuhal Walad (Dear Beloved Son). Translated by Dr. Kamal El-Helbawy. Al-Ghazali is known as Hujjatul Islam (Proof of Islam).
"Imam al-Ghazali (1058 - 1111 CE) offers advice that are of paramount importance. In analysing the human psyche, he is undoubtedly a master. He covers topic such as sincerity, knowledge, action, death, dakwah, hypocrisy, time, zikir, Shari'ah, in such delicacy and coherency that one is able to grasp clearly the multi dimensional facets of a comprehensive Islam. It seems as though this piece of work (Ayyuhal Walad) is a synopsis of his magnum opus Ihya' Ulumal-Din." - S M Hasan al-Bana.