The Targum's gloss here is theologically sharp. From the time he appointed him superintendent over his house, and over all that he had, the Lord prospered the house of the Mizraite for the sake of the righteousness of Joseph (Genesis 39:5).
Notice what Pseudo-Jonathan does with the Hebrew. The biblical text says simply, the Lord blessed the Egyptian's house on account of Joseph. The Targum sharpens the cause: it was not Joseph's presence that drew the blessing but zechut Yosef — the merit of his righteousness. The Aramaic insists the blessing is earned character, not ambient magic.
This is one of the earliest rabbinic statements of an idea the Sages return to often. The righteous are a vessel; when one stands in a household or a city, the rain of heaven falls on that place differently. Abraham's presence caused Laban's household to prosper through Jacob. Jacob's presence caused Laban's flocks to multiply (Genesis 30:27). Now Joseph's presence causes Potiphar's entire estate — fields, storehouses, livestock — to flourish. In the house and in the field, the Targum specifies: both indoor commerce and agricultural yield.
The Sages were careful with this idea. It does not mean the righteous are talismans or that exploiting them is rewarded. It means something more uncomfortable: the moral quality of the people we depend on shapes the material yield of our lives. Potiphar did not convert. He did not know what made his barns full. But the Lord of Joseph was not indifferent to Joseph's honesty, and the house benefited.
The takeaway reaches in two directions. To the one living in exile: your integrity, quietly kept, is already blessing the place that does not recognize you. To the one who benefits from a righteous servant, friend, or employee: much of what you count as your own fortune is borrowed light. Handle the person who carries it with care.