The Messenger of Allah (صلى الله عليه وسلم) loved to begin with the right side as long as he could, in wearing shoes, combing his hair, cleaning or washing himself and doing anything else.
The Messenger of Allah (صلى الله عليه وسلم) said:
“Mention the name of Allah and eat with your right hand and eat from what is near you.”
“Those who are on the right have preference, then again the ones who are on the right.”
“None of you should eat with his left hand and drink with that (left hand), for the Satan eats with left hand and drinks with that (hand). Do not take up anything with that (left hand) and do not give anything with that.”
“Indeed, Allah loves in everything to be started with the right (side).”
“Start with the right side even in wearing the shoes and combing the hair.”
Az-Zuhari (رضي الله عنه), on the authority of Anas Ibn Malik (رضي الله عنه) narrated:
“I milked a domestic sheep for the Messenger of Allah (صلى الله عليه وسلم) which was in the house of Anas Ibn Malik. Its milk was mixed with water from the well in the house of Anas. He gave the Messenger of Allah (صلى الله عليه وسلم) the cup and he drank from it and then lowered it from his mouth. Abu Bakr (رضي الله عنه) was on his left and a Bedouin on his right. `Umar (رضي الله عنه) said, being afraid that he would give it to the Bedouin, ‘Give it to Abu Bakr (رضي الله عنه) who is with you, O Messenger of Allah! He gave it to the Bedouin who was on his right and said: ‘The right, then the right.”
There is also a Hadith about a man who ate with the Messenger of Allah (صلى الله عليه وسلم) using his left hand, and the Messenger of Allah (صلى الله عليه وسلم) said: “Eat with your right hand.” He said: “I cannot.” He said: “Then you cannot.” Only pride had stopped him.” The narrator says: “He could not raise it to his mouth.”
The reasoning is based on the fact that the meaning of the Hadith is coinciding with scientifically proven reality- as they said – that every movement in the human body, rotates according to an accurate system. The movements start from the right to the left until it dwindles and ends, they gave some examples for this; including the following:
1 – The Circulation of Blood : the first drop of blood within the circulatory system starts from the right side, when the muscles of heart shrink to pump the blood, circulation of pure blood begins through the ventricles of heart into the aorta and heads from the right to the left in a curved form, thus the blood flows beginning from the right and moves to the left, as the vascular arteries diverge and branch out from thin to thinner until the blood flow decreases and becomes invisible to the naked eye.
2 – The Movement of Foodstuffs in the Intestines: As the foodstuffs start their moves from the opening of duodenum, so the direction of moving foodstuffs becomes from the right to the left.
3 – The Movement in the Colon: the movement in the large intestine starts from a point in the right side towards the left, when it shrinks to push the remaining food material to the opposite left side after the process of absorption, having accumulated in the large reservoir in the stomach. Thus, the remnant materials move from the right to the left than to the parallel transverse colon, and so on.
4 – Movements of Neural Alerts: the movements of neural alerts in the nerve centers and sensory related nerves are weird and wonderful in creation. These movements also start from the right and end on the left side, when performing their normal physiological function.
The above mentioned scholars view that the Hadith has indicated to this scientific phenomenon in the human entity, which was discovered only after the passage of many centuries on this prediction by the Prophet (صلى الله عليه وسلم).
If their reasoning is accepted, perhaps the best way for this meaning is to formulate the expression as follows: The Prophet (صلى الله عليه وسلم) was sent by Allah the Almighty with this great religion, the religion fully coinciding with human nature. Amongst its teachings is the principle of starting any auspicious work with the right side, while it has been scientifically proven that the system of human body was created on the principle of ‘right-sidedness’ in the movement of organs, thus the teachings of the religion coincide with the natural system of the creation. So it is among the miracles of the Prophet (صلى الله عليه وسلم) as the teachings introduced by him are coinciding with the system of Allah establish in His creatures and Allah knows best.
It should also be noted that the right organs are stronger than the left; so it is appropriate to be preferred. But who contemplates in those Hadiths will find that the devil prefers his left; with it he eats, with it he drinks, with it he takes and with it he gives. That is why it is more preferable for a Muslim to differ from the devil and he was ordered by Shari`ah to start with the right side.
Al Qurtubi said: “This etiquette is preferable and it is a sort of honoring the right on the left; because mostly they are stronger, faster in action and more perfect in the works. Furthermore, the word ‘Tayamun’ (the right-sidedness) was derived from ‘Yumn’ (auspiciousness) and the people of Paradise were honored by Allah the Almighty as they were attributed to the ‘Yamin’ (right side) while the people of Hell were ascribed to the left.
In short, the ‘Yamin’ (or the right) and whatever has been ascribed to it and its derivatives are auspicious in the terms of language, religiosity and devoutness while the left is opposite of these good qualities. After this point has become clear, it is among the appropriate etiquettes that coincide with good morals and good ethics especially in the sight of meritorious people to prefer always the right side in auspicious actions and clean conditions.”