The Lord stood by him - Evidently the Lord Jesus. See the notes on Acts 1:24. Compare Acts 22:18. The appearance of the Lord in this case was a proof that he approved the course which Paul had taken before the Sanhedrin.

Be of good cheer - It would not be remarkable if Paul, by these constant persecutions, should be dejected in mind. The issue of the whole matter was as yet doubtful. In these circumstances, it must have been especially consoling to him to hear these words of encouragement from the Lord Jesus, and this assurance that the object of his desires would be granted, and that he would be permitted to bear the same witness of him in Rome. Nothing else can comfort and sustain the soul in trials and persecutions but evidence of the approbation of God, and the promises of his gracious aid.

Bear witness also at Rome - This had been the object of his earnest wish Romans 1:10; Romans 15:23-24, and this promise of the Lord Jesus was fulfilled, Acts 28:30-31. The promise which was here made to Paul was not directly one of deliverance from the present persecution, but it implied that, and made it certain.

Acts 23:11 Parallel Commentaries

Whether Discord is a Sin?
Objection 1: It would seem that discord is not a sin. For to disaccord with man is to sever oneself from another's will. But this does not seem to be a sin, because God's will alone, and not our neighbor's, is the rule of our own will. Therefore discord is not a sin. Objection 2: Further, whoever induces another to sin, sins also himself. But it appears not to be a sin to incite others to discord, for it is written (Acts 23:6) that Paul, knowing that the one part were Sadducees, and the other Pharisees, …
Saint Thomas Aquinas—Summa Theologica

The Life and Death of Mr. Badman,
Presented to the World in a Familiar Dialogue Between Mr. Wiseman and Mr. Attentive. By John Bunyan ADVERTISEMENT BY THE EDITOR. The life of Badman is a very interesting description, a true and lively portraiture, of the demoralized classes of the trading community in the reign of King Charles II; a subject which naturally led the author to use expressions familiar among such persons, but which are now either obsolete or considered as vulgar. In fact it is the only work proceeding from the prolific …
John Bunyan—The Works of John Bunyan Volumes 1-3

How Sowers of Strifes and Peacemakers are to be Admonished.
(Admonition 24.) Differently to be admonished are sowers of strifes and peacemakers. For sowers of strifes are to be admonished to perceive whose followers they are. For of the apostate angel it is written, when tares had been sown among the good crop, An enemy hath done this (Matth. xiii. 28). Of a member of him also it is said through Solomon, An apostate person, an unprofitable man, walketh with a perverse mouth, he winketh with his eyes, he beateth with his foot, he speaketh with his finger, …
Leo the Great—Writings of Leo the Great