Komentarz do Powtórzonego Prawa 23:14

על אזנך [AND THOU SHALT HAVE A PIN] על אזנך — i.e. besides (על, “in addition to”, not “upon”) your other implements.

על אזניך, in addition to your other equipment.

ויתד תהיה לך על אזנך, “you are to have a shovel in addition to your gear (weapons).” The letter א at the beginning of the word אזנך is an addition, not part of the root. The basic word is זין, weaponry. The shovel is supposed to be an integral part of your equipment in war, no less important than your weapons. This commandment reflects he spiritually high level of a Jewish camp. It reflects the awareness by the Jewish soldiers that the Shechinah is in their midst. At the same time, the need for the shovel indicates that the Torah speaks of a period when the people had already become guilty of sins seeing that during the years when they did not sin there was no need for a shovel as the manna was completely absorbed by their bodies so that there was no excrement which had to be covered up. Not only that, but it also absorbed the taste of other foods. After the Israelites had begun to sin, they did need shovels to clean up after themselves. I have already discussed this matter in Numbers 11,5.
Our sages in Yuma 75 explain that when the Israelites defecated they did not do so sideways or forwards but behind themselves so as not to expose their excrement to the clouds of glory which accompanied the Israelites on both their flanks and in front of them.