What is Yesad?
Rashi: It is a peg.
What is Makeves?
Rashi: It is a hammer.
What is the meaning of "va'Titznach"?
Rashi, Radak, citing Targum Yonasan: [The peg passed through his head and] was inserted [in the ground].
If the peg was inserted in his head, how was it inserted in the ground?
Malbim: She took the hammer in one hand and the peg in the other. She did not have enough strength to strike the hammer on the peg; Hashem helped that the peg pierced his head and entered the ground due to its own weight.
What is the meaning of "Nirdam va'Ya'af"?
Radak: He fell asleep because he already was tired (so he did not feel when she struck him). This is unlike "va'Ya'af" in Yeshayah 6:6 (with a Kamatz under the Ayin; it is an expression of flying).
How could Ya'el kill Sisera? There was Shalom between Yavin and Keini!
Malbim, based on Mahari Kara #1: Chever separated from the other Keinim to live among Yisrael, so he need not guard the Bris of the Keinim.
Malbim, citing Mahari Kara #2: Women are not bound by agreements between nations. She killed him; her husband did not!
Malbim: Chever was from Bnei Yisrael. Surely he must fight against Sisera together with them!
Why did the salvation come via Ya'el?
Tana d'Vei Eliyahu Rabah (10): She was a Kosher woman, and did her husband's will.
