John Gill Commentary Acts 28:21

"And they said unto him, We neither received letters from Judaea concerning thee, nor did any of the brethren come hither and report or speak any harm of thee." — Acts 28:21 (ASV)

And they said to him
That is, the chief men of the Jews at Rome, whom Paul had called together, replied; either in a lying and dissembling way, or as expressing matter of fact; which last may be allowed:

we neither received letters out of Judea concerning you :
which was very much, that the high priest and sanhedrim had not wrote to the principal men of their religion at Rome; giving an account of the apostle, and his case to them, in order to prejudice them against him, and to furnish them with charges and accusations; which if they could not prevail by them, so as to get him condemned by the emperor, yet might be a means of preventing any of their nation giving heed unto him, and embracing his sentiments and notions concerning Jesus of Nazareth:

neither any of the brethren that came [from] Jerusalem ;
or any part of Judea, to Rome; meaning not the Christian Jews, for these they would not call brethren; but those who were of the same religion as well as nation, whom it was usual with the Jews to call brethren:

shewed or spoke any harm of you ;
so that it looks as if they did make mention of him, but did not charge him with anything that was wicked and criminal: this they said, to show that they were not prejudiced against him by any person or means; and which carried in it a very considerable testimony of the apostle's innocence.