The Targum sees Tamar at a moment of ruined expectation. Judah had promised her his youngest son, Shelah, after her two husbands had died in sequence. She waited. She waited longer. And when she saw that Shelah had grown up and still she had not been given to him (Genesis 38:14), she understood that her place in the family of Israel was being quietly withheld.
So she acted. She stripped off her widow's garments — the uniform of a woman without claim — and wrapped herself in a veil. The Aramaic says she sat be-parashat orchin, at the parting of the roads, where all eyes see. This is not the hiding place of a harlot. This is a deliberate, visible waiting, on the road to Timnath where Judah would pass. The Targum stresses: she knew exactly where she was and why.
What the tradition preserves is Tamar's moral logic. The line of the future House of David — Perez, Boaz, Jesse, David, and ultimately the Messiah — had to pass through her. The family had forgotten its promise; she would remind it. She veils herself not to disappear but to insist, through disguise, on being seen.
The Sages in Bereshit Rabbah 85 read her sitting at the crossroads as a prayer posture. She lifted her eyes, they say, and asked that she not return from this road empty. The Targum Pseudo-Jonathan (redacted in the centuries after the Temple's destruction) pushes the reading further: Tamar is already conscious she is carrying the line of kingship on her shoulders, and she is willing to look, for a moment, like exactly what she is not, so that her people's future can be born.
The takeaway is quiet and sharp: sometimes righteousness wears a veil, and what looks scandalous from the road is, from heaven, the long turning of the promise.