In fact, the practice of doing certain things using the right hand and doing other things using the left is confirmed by the Prophetic Sunnah. So, it is more akin to the way the Prophet, peace and blessings be upon him, set for his followers.
The prominent Saudi Islamic lecturer and author, Sheikh Muhammad Saleh Al-Munajjid, states: “A person who uses his left hand in eating and drinking should be taught the Islamic ruling and should be reminded of the Hadith of the Prophet, peace and blessings be upon him, on this matter.
When a man ate with his left hand in the presence of the Prophet, peace and blessings be upon him, he told him: “Eat with your right hand.” (Reported by Muslim)
The Hadith encourages us to teach proper manners of eating to a person who fails to abide by Islamic ethics of eating. Besides, eating and drinking with left hand is the habit of the Satan; this is clarified by the following Hadith: “When any one of you eats, let him eat with his right hand, and when he drinks, let him drink with his right hand, because the Satan eats with his left hand and drinks with his left hand.” (Reported by Muslim).
Satan eats with his left hand so a person eating with his left hand resembles Satan, and he indeed allows Satan to share food with him. `Aishah, may Allah be pleased with her, quoted the Prophet, peace and blessings be upon him, as saying: “Whoever eats with his left hand, the Satan eats with him.” (Reported by Imam Ahmad).
Moreover, the left hand should be reserved for removing dirt, cleaning oneself after going to the toilet and blowing one’s nose and other kinds of cleaning oneself and removing dirt. How can a person use that which is used for removing dirt and impurities for putting food in his mouth?
Hafsah, may Allah be pleased with her (the wife of the Prophet, peace and blessings be upon him) stated that the Prophet, peace and blessings be upon him, used to use his right hand for eating, drinking and getting dressed and his left hand for everything else. (Reported by Abu Dawood).
Imam An-Nawawi, may Allah have mercy on him, said: “This is a fixed rule in Shari`ah. The right hand has to do with honorable things such as putting on one’s shirt, trousers and shoes, entering the mosque, using Siwak, applying kohl, combing and styling one’s hair, shaving the head, washing oneself in Ghusl (body-washing) and Wudu’ (ablution), leaving the toilet, eating, drinking, shaking hands, touching the Black Stone, and other things where we are encouraged to use the right hand or start with the right.
As for the opposite ( i.e., things that are not honorable), such as entering the toilet, leaving the mosque, blowing one’s nose, washing oneself after using the toilet, taking off one’s shirt, trousers and shoes, and so on, then we should start with the left or use the left hand. All of this has to do with honoring the right hand or right side.”
However, some people may have a real problem that prevents them from using their right hand, such as being paralyzed and so on. In this case they are excused and there is no blame on them. Imam An-Nawawi, may Allah have mercy on him, said: “If one has an excuse for not eating and drinking with his right hand, such as sickness or an injury, then this is not Makruh (blameworthy)…”