First fruit (aparchē). See note on 1Co 15:20, 1Co 15:23. The metaphor is from Num 15:19. The lxx has aparchēn phuramatos, first of the dough as a heave offering.
The lump (to phurama). From which the first fruit came. See note on Rom 9:21. Apparently the patriarchs are the first fruit.
The root (hē riza). Perhaps Abraham singly here. The metaphor is changed, but the idea is the same. Israel is looked on as a tree. But one must recall and keep in mind the double sense of Israel in Rom 9:6. (the natural and the spiritual).