From Sensus Plenior
all, any, every, he contains כל
- כ-ל - Son of God כ teaches ל. "All in all" refers to the Son of God being the teacher or testimony in all creation. 
- 1Co 15:28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.