The interdependence of the heart and the body, and likewise of the outward and the inward.

The Shaykh : ... this sincere heart is sound, and the opposite is the opposite entirely, . Therefore—and the research into this is long and very long—Muslims must not be deceived by the statement of some who say that what matters is what is in the heart, as a deception of the people. We say with them: what matters is what is in the heart, but we add to them and say: it is not possible for what is in the heart to be sound and for corruption to appear from the body, and the opposite is the opposite; it is not possible for what is in the heart to be corrupt and for soundness to appear from the body; this is a matter that is not sound and not correct at all.
The case of this is like the case of the heart and the body from the medical perspective; if the heart is sound, it is not possible for the heart to be sick, and the opposite is also the opposite; if the heart is sick from the medical perspective, it is not possible for the body to be sound. This is a consistent matter, negatively and positively, in physical medicine and prophetic medicine. So those who say, when they are commanded—for example—to perform the prayers or to maintain them, they tell you: "My brother, the matter is not about what is in the prayer, the matter is about what is in the heart." We say: You are correct, the matter is about what is in the heart, but if what is in the heart were correct, sound faith, this heart would overflow with soundness, obedience, and worship; otherwise, the matter is the opposite entirely, and the matter is as it was said:
"So this difference between us is sufficient for you, *** And every vessel overflows with what is in it."
So if this vessel that Allah (Mighty and Majestic) placed in the chest with great care and wisdom is sound and healthy, there is no doubt that it will overflow with soundness and health, and the opposite is the opposite. I said: this research has a long tail, and I am content with this amount to direct attention to the fact that closeness in the circles of dhikr and knowledge is a desirable, prescribed matter, and the distancing of some of the sitters from one another is—as you heard—from the work of Satan. Come closer as much as you can.