82 διαμαρτύρομαι 1 has “testify of, bear witness to (orig. under oath) … of repentance to Judeans and Hellenes Ac 20:21.”
83 Several , including some of the more important ones (𝔓74 א Α C [D] E 33 36 323 945 1175 1241 1505 1739 and a number of versions), read Χριστόν (Christon, “Christ”) at the end of this verse. This word is lacking in B H L P Ψ 614 . Although the inclusion is supported by many earlier and better , internal evidence is on the side of the omission: In Acts, both “Lord Jesus” and “Lord Jesus Christ” occur, though between 16:31 and the end of the book “Lord Jesus Christ” appears only in 28:31, perhaps as a kind of climactic assertion. Thus, the shorter reading is to be preferred. Repentance toward God and faith in our Lord Jesus. Note the twofold description of the message. It is a turning to God involving faith in Jesus Christ.

In other versions

testifying both to Jews and to Greeks of repentance toward God and of faith in our Lord Jesus Christ.

I have declared to both Jews and Greeks that they must turn to God in repentance and have faith in our Lord Jesus.

I testified to both Jews and Greeks about repentance toward God and faith in our Lord Jesus.

I have had one message for Jews and Greeks alike—the necessity of repenting from sin and turning to God, and of having faith in our Lord Jesus.

testifying both to Jews and to Greeks with respect to repentance toward God and faith in our Lord Jesus.

Testifying both to the Jews, and also to the Greeks, repentance toward God, and faith toward our Lord Jesus Christ.

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