1)
Why are all hands soft?
1.
Radak: They will not have strength to fight against all the enemies.
2)
How are knees "Telachnah Mayim"?
1.
Rashi: They sweat amidst fear.
2.
Radak: Telachnah k'Mayim. This is a Mashal. It is as if they melted. They have no strength, amidst frenzy. Malbim - they cannot fight due to softness of hands, nor flee due to weakness of knees!