What are "Sechireha"?
Rashi, Targum Yonasan: They are Sareha (its officers), like "b'Sa'ar ha'Sechirah" (Yeshayah 7:20).
Radak: The troops that they hired to help them are inside [Egypt].
Malbim: They are kings who fought for wages; they helped Egypt.
What is "Marbek"?
Rashi: It is a stall for calves [to fatten them - Rashi Mal'achi 3:30].
Radak: They are calves in the house to fatten them 1 . So they (the troops hired to help them) sit, eat and drink and do not go out to fight.
Radak: The same applies to "Egel Marbek" (Shmuel I, 28:24). We find 'Hichnisah l'Ravkah' (Pesachim 26a; a place where it is tied to cows).
Why does it say "Hifnu"?
Rashi: They turned Oref (the back of their necks, towards the enemy) and sought to flee.
Malbim: The kings who fought for Egypt for wages are compared to calves that were there to be fattened from all the good of Egypt. After the fall of the [beautiful] calf, i.e. Egypt, also they turned to go to their lands.
Why did they flee?
Malbim: "Yom Eidam Ba" - also they will be punished for their sins.
