Two interesting comments on last week's Torah reading from R. Yehuda Henkin's Chibah Yeseirah, published in the back of Responsa Bnei Banim vol. 2 (my translation):
38:25 [When she (Tamar) was brought forth, she sent to her father-in-law, saying:] "By the man to whom these belong, I am pregnant."
Those who were there recognized that the signet belonged to Yehudah, and she [Tamar] intended to save herself in that way. And one can know this in that Yehudah said "She has been more righteous than I." Why didn't he explain how she was more righteous than he and why she did not deserve to be executed? Rather, since she said "By the man to whom these belong, I am pregnant" and everyone knew that the signet was his, once he confirmed her words he confirmed that he was the fathe. However, Tamar did not name him explicitly in order to minimize his embarrassment, and also since the main prohibition of embarrassing someone is verbally (see Bnei Banim 1:41).
39:1 [And Joseph was brought down to Egypt; and Potiphar, an officer of Pharaoh's, the captain of the guard,] an Egyptian[, bought him of the hand of the Ishmaelites]
Would we think that he was Assyrian or Persian? Rather, in that generation foreigners ruled in Egypt. It is told in the histories of Egypt, and cited in Josephus' book, that a Semite tribe from the north came and ruled over Egypt for approximately 100 years. The king and all of his ministers were from that tribe but Potiphar was an Egyptian. He was appointed captain of the guard, who takes out [prisoners] to be executed and is responsible for the prisons, as it says (Gen. 41:10) "in the ward of the house of the captain of the guard." [He had this position] because it was better for the foreign rulers that the executioner be a native citizen, so the people hate him and not them.