Maimonides, in his Mishna Torah compilation, explains that Jacob separated his son Levi from his other sons and appointed him to instruct and teach the ways of "service to God", specifically the servicial methods used by his forefather Abraham, to his brothers. He also instructed his sons to perpetuate this status of Levi ("Shevet Levi") for eternity (Maimonides, Avodah Zorah 1:15). For the prelude of this choice see Targum Yonathan to Genesis 32:25, and/or Pirkei de-Rabbi Eliezer ch. 37. In midrash, it is written that Amram the son of Kohath the son of Levi was the spiritual leader of the sons of Jacob ("Israel") during their Egyptian Bondage. Following his passing, his post was assumed by his son Aaron.