Why we shouldn’t eat with our left hand?
Allah has commanded that men must observe the difference between the right-had side and the left-hand side. When performing ‘pure’ actions (such as eating, drinking, putting on clothes) the right hand and the right-hand side must be preferred, while for the performance of ‘impure’ actions (such as intimate hygiene, nose blowing, taking off clothes) preference should be given to the left hand or the left-hand side. This requirement is not a fard (i.e. it is not a must). Rather, it appeals to those who wish to distinguish themselves in front of the Lord in a supererogatory way, to please Him better than any other men on top of the obligatory things they do in the normal course of worship. Such piety is a much laudable thing.
The sides being defined as ‘pure’ and ‘impure’ is a reflection of Islam’s concept of purity as such.
All things pure are Halal, all things impure are Haram. Men must strive for the things that are Halal. For the sides (and the hands) this is a convention to make this strife for Halal easier to achieve and, as it were, mostly ‘technical’.
Like the difference between rooms in an apartment; bedrooms are for sleeping, bathrooms for washing and dining rooms for eating. This doesn’t mean that we cannot have dinner in the bedroom or wash in a bowl at the kitchen. This is not prohibited but this will look weird. Similarly, the difference between the ‘pure’ and the ‘impure’ hand is a convention to help us remember piety and to be sure we are not transgressing against cleanness.
It is just that we shall at all times remember that the right hand does clean things and the left hand is reserved for the dirty things.
This way men may leave aside doubts: anything coming your way from the right is pure and pleasing to Allah, anything coming your way from the left is vice versa.
The Prophet observed this testament and admonished others to do likewise. The Prophet’s third wife Aisha thus described her husband’s ways; “The Messenger of Allah liked to begin with the right side as far as possible in all conditions: in his purification, and combing.” (Sunan Abu Dawood, 4140) The Prophet himself thus told his companion Ibn Umar, the son of Caliph Umar; “When any of you eats, he should eat with his right hand, and when he drinks, he should drink with his right hand, for the devil eats with his left hand and drinks with his left hand.” (Sunan Abu Dawood, 3776)
These testaments are meant to help men keep up their piety.
But what if a pious and God-loving man cannot follow them fully because for him the left-hand side is preferable to the right-hand side? By this we mean left-handers.
They are entitled to amendments to this rule. For left-handers did not make themselves left-handed, it was Allah Who made them such, hence it was Allah Who commanded them to use their left hands for picking up food and drinks. Therefore, for such people the functional designation of their hands shall be reversed. What others do with their right hands, left-handers shall do with their left hands. And this will be in strict conformity with Allah’s Will.