Final answer:
Judah asked Tamar to wait as a widow at her father's house until his third son grew up, out of fear that Shelah might die like his siblings.
Step-by-step explanation:
After the death of Judah's second son, Onan, the story in the biblical text does not provide specific dialogue between Judah and his daughter-in-law Tamar about this event. However, the biblical narrative in Genesis 38 tells us that Judah asked Tamar to wait as a widow in her father's house until his third son, Shelah, grew up, fearing that Shelah would die like his brothers if married to Tamar. In the context of inheritance and family lineage, this situation reflects the practices and customs of the time.