Why did Yehudah agree to give a kid-goat, and the three objects as security? Why did Yehudah not simply pay her fee?
Oznayim la'Torah: Yaakov initiated a system of coins in Shechem, implying that other towns still employed the system of bartering goods. 1 Consequently, Yehudah offered Tamar a kid-goat, and three personal objects as security until it was available.
There were coins before this! Avimelech gave money when he returned Sarah. Avraham bought Sedeh Efron for "coins accepted in all places" (20:16, 23:16). Midrashim discuss how Sodomites would give marked coins to a poor man, and then take them back after he died; Lavan embraced Yaakov to feel for coins... (PF) Maharsha (to Shabbos 33b) explains that Yaakov minted coins with the image of the city on them.
"Anochi Ashlach Gedi Izim." Why does the Torah insert the (otherwise superfluous) word "Izim"?
Chulin 113a-b: To teach us that, wherever the Torah writes "Gedi" without specifying, 1 it includes the young of any species, whether calf, lamb, or kid goat.
E.g., regarding the prohibition of meat with milk, "Lo Sevashel Gedi etc." (Shemos 23:19).
Why did Yehudah add the (otherwise superfluous) word "Anochi"?
Ha'amek Davar: The value of an Esnan depends on the status of the Bo'el. A Bo'el of lesser status would have had to pay more. Yehudah pointed out that for a man of his status, a kid-goat would suffice.
