Lit., working together. With Him is implied in the compounded ούν with. That it refers to God, not to the fellow-Christians, is evident from the parallel 1Co 3:9, laborers together with God, and because the act of exhortation or entreaty in which the fellowship is exhibited is ascribed to God in 2Co 5:20. The phrase Θεοῦ πάρεδροι assessors of God, occurs in Ignatius' letter to Polycarp. Compare Mar 16:20.
In vain (εἰς κενὸν)
Lit., to what is vain. Equivalent to the phrase to no purpose.