The Targum closes the chapter with a line that the Sages read as the key to the whole Joseph narrative. It was not needful for the captain of the prison to watch Joseph, after the custom of all prisoners, because he saw that there was no fault in his hands; for the Word of the Lord was his Helper, and that which he did the Lord made it to prosper (Genesis 39:23).
The Aramaic phrase is Meimra d-Ya — the Word of the Lord. Pseudo-Jonathan uses Meimra throughout its translation of the Torah as a way of naming God's active presence in the world without, as the Targum is careful to do, speaking of God's body or physical proximity. The Meimra is God's speech made effective — the Word that was with Abraham (Genesis 15:1), the Word that spoke with Jacob (Genesis 28:13), the Word that will speak with Moses from the bush (Exodus 3:4).
The Targum is saying: Joseph was not alone in the prison. The same Meimra that stood with his fathers stood with him in the lowest place in Mizraim. The warden saw what he could see — a young man whose work bore no fault — but the Targum reveals what he could not see: a Helper behind the helper.
Bereshit Rabbah 87 expands this further. The Lord made it to prosper is not about material luck. It is about the way every small task Joseph undertook in the prison — the ledger of inmates, the cups of water, the conversations at night — was being braided by heaven into a longer plan. None of it looked significant on the day it was done. All of it was necessary.
The takeaway is one of the oldest comforts in the Jewish tradition. The righteous person in the worst place is not abandoned. The Word that spoke the world into being also keeps company with the prisoner who refuses to let the prison change him. What he did the Lord made to prosper — not because the work was large, but because the Word was with the worker.