About three months later, Yehudah was told, “Your daughter-in-law Tamar has played the zonah; in fact, she is pregnant from zenunim.” “Bring her out,” said Yehudah. “She should be burned!”
It was taught: Sumchus says in the name of R’ Meir: A fetus is recognizable at three months. And although there is no [decisive] proof for the matter, there is a mnemonic for the matter, as it is stated: “And it was at about three months.”
On the daf / in context: Niddah uses Tamar’s pregnancy report as a zecher for the three-month visibility of pregnancy.
Type of Learning
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. Narrative timing supplies a halachic mnemonic.
What Is Learned
A pregnancy may be recognized at three months; the story of Tamar is cited as a scriptural reminder of that span.