Jamieson, Fausset & Brown

Translate, as the Greek collocation of words, and the emphasis on "God" thrice repeated, requires, "For (in proof that "each shall receive reward according to his own labor," namely, from God) it is of God that we are the fellow workers (laboring with, but under, and belonging to Him as His servants, Co2 5:20; Co2 6:1; compare Act 15:4; see on Th1 3:2) of God that ye are the field (or tillage), of God that ye are the building" [ALFORD]. "Building" is a new image introduced here, as suited better than that of husbandry, to set forth the different kinds of teaching and their results, which he is now about to discuss. "To edify" or "build up" the Church of Christ is similarly used (Eph 2:21-22; Eph 4:29).