“Whoever is fearful and trembling.” God told Israel not to be fearful going into battle (Deut. 20:1-9). If part of the army is fearful, it can ruin the moral of the rest of the army.
“from Mount Gilead.” The Ein Harod spring is at the foot of Mount Gilboa, whereas “Gilead” is in the Transjordan. It is possible that here the Hebrew word “Gilead” is translated from a root that can mean “afraid,” and that this is related somehow to being afraid. There are other possibilities as well, one being that there was a mountain referred to as Gilead that was close by but which is now unknown.