Rashi on Genesis 38:25/רש"י על בראשית ל״ח:כ״ה

1הוא מוצאת WHEN SHE WAS BROUGHT FORTH to be burnt.

2והיא שלחה אל חמיה SHE SENT TO HER FATHER-IN-LAW — she did not wish to put him to shame in public by saying “It is by thee that I am with child”, but she said only “By the man whose these are”. She thought: “if he is to acknowledge it, let him acknowledge it voluntarily, and if not, let them burn me and let me not put him to shame in public”. From this passage our Rabbis derived the teaching: Far better that a man should let himself be cast into a fiery furnace (even as Tamar was ready to be burnt to death) and let him not publicly put his fellow to shame (Sotah 10b).

3הכר נא RECOGNISE, I PRAY THEE — The word נא is used as an expression of entreaty: Acknowledge (הכר) I beg of you, your Creator and do not destroy three lives (Genesis Rabbah 85:11).