narrated 'umar bin abi salama (radi-allahu 'anhu):

i was a boy under the care of allah's apostle (sallallahu 'alaihi wa sallam) and my hand used to go around the dish while i was eating. so allah's apostle (sallallahu 'alaihi wa sallam) said to me, 'o boy! mention the name of allah and eat with your right hand, and eat of the dish what is nearer to you.' since then i have applied those instructions when eating.

bukhari vol. 7 : no. 288