Jamieson, Fausset and Brown on Acts 23:11

Ac 23:11-35. In the Fortress Paul Is Cheered by a Night Vision--An Infamous Conspiracy to Assassinate Him Is Providentially Defeated, and He Is Despatched by Night with a Letter from the Commandant to Felix at Cæsarea, by Whom Arrangements Are Made for a Hearing of His Cause.

11. the night following--his heart perhaps sinking, in the solitude of his barrack ward, and thinking perhaps that all the predictions of danger at Jerusalem were now to be fulfilled in his death there.

the Lord--that is, Jesus.

stood by him ... Be of good cheer, Paul; for as thou hast testified of me in Jerusalem, so must thou ... also at Rome--that is, "Thy work in Jerusalem is done, faithfully and well done; but thou art not to die here; thy purpose next to 'see Rome' (Ac 19:21) shall not be disappointed, and there also must thou bear witness of Me." As this vision was not unneeded now, so we shall find it cheering and upholding him throughout all that befell him up to his arrival there.