Sarkinos or Sarkikos

[In verses 1 and 3] Paul uses two different words. The word used in verse 1 is sarkinos and the one used twice in verse 3 is sarkikos. Some see no difference in the meaning of the two words, but probably most do. If there is a difference, it is this: Sarkinos means “made of flesh,” that is, weak but without attaching any blame to that condition. In the case of the Corinthians, their weakness was due to their immaturity.

On the other hand, sarkikos does have an ethical or moral connotation. It means “to be characterized by the flesh, something that is willful and blameworthy.” The first word means “made of flesh,” while the second means “controlled by the flesh.”

So Great Salvation, Charles Ryrie, Victor Books, 1989, p. 61.