The Targums are old Aramaic translations of the Hebrew Bible. Like the LXX, they were written for ancient communities of Israelites who no longer spoke Hebrew as their native language, and like the LXX, they can differ significantly from the MT. Sometimes the differences come because of error, but often the differences come because the translators understood the Hebrew passage differently than we do and inserted commentary, or because they were looking at a more ancient and different Hebrew text than we have today.
You can read English translations of the Targums online here. You can also buy physical books on Amazon.
I have observed that Genesis and Moses both seem to identify Cain as a priest. It turns out that the Targum Pseudo-Jonathan adds another element that suggests we should think of Cain this way. At this link you can find the first six chapters of Genesis; scroll down to chapter IV and read the Targum's translation of Genesis 4:1:
And Adam knew Hava his wife, who had desired the Angel; and she conceived, and bare Kain; and she said, I have acquired a man, the Angel of the Lord.
The Angel Eve desired in the Targum was Sammael, the angel of death, who appeared in Genesis 3 beside the tree of knowledge as Eve ate. But the man Eve acquired, the Angel of the Lord, is Cain. Remember: stars = angels = priests.