Reference: Fataawa ash-Shaykh Ibn Humayd – Page 276, Question No.291
Question: After finishing eating food, a person takes to fruit; he picks it up with his right hand, and as a result some food remains [from his right hand] fall on the fruit, and the people dislike this. So is there any harm in eating this fruit with the left hand?
Response: It is not permissible for a person to eat with his left hand, as the Prophet (sal-Allaahu ‘alayhi wa sallam) said to the young boy:
«O young boy! Mention the name of Allaah and eat with your right hand, and eat of that which you can chew».
So, if he fears some food remains from his right hand will fall on the fruit, then he should pick up the fruit with his left hand and eat it with his right hand.
And this is what the people of knowledge have dictated. And Allaah [alone] has the Complete knowledge [of all affairs].