There are a number of things in relationship to his hand gesture.
When the Gospel is open Christ is teaching.
When it is closed Christ is blessing.
The fingers tell you two things:
The two fingers speak of his two natures - God and Man.
The three fingers are the Trinity
Then:
The index finger held straight, makes the "I," the middle and little fingers are curved into "C" shapes, and the thumb and ring finger cross slightly forming the "X," making Christ�s name, "IC XC."
This is the shape our priests use today to bless us with not with the open hand you see from with the Roman Rite priests.
