Al-Ahzab (The Confederate Tribes)
Chapter 33: Verse 4 (partial)
Man cannot have one source for his manners and morality, another for his laws and legislation, a third for his social and economic values, and a fourth for his art and philosophy. Such a mixture does not produce a man with a sound heart: it only produces a confused medley that lacks solid form or basis. A person with faith cannot truly hold to his faith and abandon its values and requirements in any situation in life, serious or not. He cannot say a word, take an action, formulate a concept, make a decision unless he remains within the limits established by his faith, which must always be a reality in his life. This is because God has not given him more than one heart, one law and one standard of values. A person of faith cannot say of anything he does: 'I am doing this in my personal capacity and I am doing this in my Islamic capacity', as we frequently hear politicians, businessmen, acad emics and others say. Since he is one person with one heart, he has one faith and one standard that govern all that he does and says in any and every situation. With this one heart he lives as an individual, a family man, a member of the community, a citizen of the state and the world; he lives in public and private, employer or employee, ruler or ruled, in situations of comfort or distress; having the same values and standards at all times.
In short, we have a single system outlined by the same revelations and submitting to the One God. A single heart cannot worship two deities, serve two masters and move in two directions. Otherwise, it will be pulled apart and will have different motives and considerations. It could easily fall into the trap of hypocrisy.
"In The Shade Of The Quran" - Sayyid Qutb, Volume 14, pp. 13, 14