13:4 God’s servant for your good. The state’s authority is for society’s benefit; this is its normal function, and Paul assumes it may be realized in practical terms even when governments are professedly non-Christian.
the sword. The power of life and death. Capital punishment is undoubtedly in view. Elsewhere Paul accepts the principle of such punishment where appropriate (Acts 25:11).
wrath. What the individual must not do out of a motive of revenge (12:19), the state may legitimately do in the pursuit of justice.