Commentaries:
Robertson's Word Pictures (NT)
And severally (to de kaq eiv). A difficult late idiom where the preposition kaq (kata) is treated adverbially with no effect on the nominative case eiv like uper egw (II Corinthians 11:23). So eiv kaq eiv (Mark 14:19) and in Modern Greek kaqeiv as a distributive pronoun. But we have kaq ena in I Corinthians 14:31. The use of the neuter article here to with kaq eiv is probably the accusative of general reference, "as to each one."
Other Robertson's Word Pictures (NT) entries containing Romans 12:5:
Ephesians 4:7
Colossians 1:18
Revelation 21:21
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