The right way of sleeping:

Dear brothers, when man goes to bed, he should pay attention to the way he lies. People lie on their abdomens, backs, right sides or left sides. 

The harmful effects of seeping on abdomen: 

Those who lie on their abdomens feel difficulty in breathing,

as their backs and skeletons weigh heavily on their lungs. Besides, such type of lying is improper and inadequate, and this is how Shyatan sleeps.

The harmful effects of sleeping on one's back: 

Those who lie on their backs can breathe from the mouth but this is not healthy.

When they sleep on their back they stop the work of a very important mechanism of their body, namely, the warming and filtration of the air coming into the lungs. In man's nose, there are the turbinates with muscular arteries. When these muscles expand, they allow a great amount of blood to flow through the arteries. When the air passes along these the turbinates

and touches the great amount of blood flowing into the nose, it becomes warm, and it reaches the trachea while its temperature is 38 degrees Celsius,

even if its temperature before getting into the nose is zero degrees Celsius.

Moreover, the turbinates have a sticky substance that sticks to the dust, soot or smut carried by the air. If anything escapes the turbinates (the superior, the middle and the inferior turbinates), there are the hairs that Allah created inside the nose in order to catch alien bodies and prevent them from getting into the lungs.

It is indeed a very complicated warming and filtering mechanism that enables the air to get to the trachea filtered, warm, clean, pure and fresh.

If man sleeps on his back and breathes from his mouth, he stops the work of this highly complicated mechanism. Furthermore, watch your noses when the weather is cold. They get red.

If man breathes from his mouth, he becomes more prone to colds, his gum gets dry and retarded,

and his snoring becomes unbearable. This is because of breathing from the mouth.

Thus, sleeping on the back in not healthy.

The harmful effects of sleeping on the left side: 

Let us move to the harmful effects of sleeping on the left side. Food usually needs 2 to 4 hours to be digested, but if man sleeps on the left side of his body, digestion needs 5 to 8 hours.

This is because the right lung, which is the bigger one, presses on the heart, while the liver, which is the biggest organ of the body, remains hanging and unbalanced. On the other hand, if man sleeps on the right side of his body, the left lung, which is the smaller and the lighter one will not affect the heart, and the liver becomes stable towards the earth and digestion becomes faster.

A Prophetic Hadith confirming the right way of sleeping:

Listen dear brothers in faith, what the Prophet (PBUH) said to the Noble Companion Al-Baraa bin 'Azib: 

(Whenever you go to bed, do wudu' as you do wudu for the prayer and then lie down on your right side. Then say: 'O Allah, I turn my face to You and I entrust my affair to You.')

 
It has been said, "Sleeping on the back is the way kings sleep, sleeping on the abdomen is the way devils sleep, sleeping on the left side is how the wealthy sleep since they eat a lot, and sleeping on the right side is how the scholars and wise men sleep." Concerning this point, I would like to repeat what the Prophet (PBUH) said:  

(Whenever you go to bed, do wudu' as you do wudu for the prayer and then lie down on your right side. Then say: 'O Allah, I turn my face to You and I entrust my affair to You.')