Literal meaning = small/little monk reads scriptures, have mouth not heart.
This is a proverb about a monk who reads the scriptures, claims to be a monk etc but in his heart doesn’t really believe or practice i.e. a hypocrite.
This proverb can be used to describe someone who is forced to study for example. Many children go to University or college because their parents force them but they don’t want to be there. Or it could be used to describe people who claim to be Christians (or any faith for that matter) but get drunk, lie, commit fornication etc.
Pretty much any situation wher what comes out of peoples mouth isn’t really what they feel think or believe. Perhaps it also carries the connotation of someone who feels a little bit of pressure from parents, society or whatever to conform or say what they say but inside they don’t agree or believe.