# he is a Jew who is one inwardly, and circumcision is that of the heart

These two phrases have similar meanings. The first phrase, "he is a Jew who is one inwardly," explains the second phrase, "circumcision is that of the heart." (See: [[rc://en/ta/man/translate/figs-parallelism]])

# inwardly

This refers to the values and motivations of the person whom God has transformed.

# of the heart

Here "heart" is a metonym for the inner person. (See: [[rc://en/ta/man/translate/figs-metonymy]])

# in the Spirit, not in the letter

Here "letter" is a synecdoche that refers to written Scripture. Alternate translation: "through the work of the Holy Spirit, not because you know the Scriptures" (See: [[rc://en/ta/man/translate/figs-synecdoche]])

# in the Spirit

This refers to the internal, spiritual part of a person that "God's Spirit" changes .