As the spies embark upon their mission Moshe gives them some advice about what to look for. He says to check and see if the inhabitants are strong or weak. Rashi quotes the Midrash that Moshe gave them a trick: if the people lived in open cities this means that they are strong and can rely on their strength alone to protect themselves. If the city is heavily fortified, then you can be sure that the inhabitants are weak and they need outside help to protect themselves.
It’s an interesting theory. I’m not sure that by merely looking at the situation one would come to those conclusions. I can imagine that spies would ordinarily make the reverse conclusion based on the evidence: ie open cities are easy prey whereas fortified cities are more difficult to conquer.
I believe that there are two lessons for us from this Midrashic understanding of Moshe’s advice. First lesson is that your eyes can deceive you and you need to interpret what you see carefully and logically, taking all factors into consideration. Perhaps Moshe was already nervous about the report that the spies would ultimately bring back, so he gave an example of how facts cannot be merely reported but need to be correctly interpreted.
The second lesson involves how we understand the relationship between something’s appearance and its essence. Moshe teaches here that very often appearances belie the essence. In this case that which looked strong is actually weak and vice-versa. That holds true for many other characteristics appearances. Those that appear happy can in fact be very sad. Those that appear rich can be very poor. Those that appear kind can in fact be very cruel.
Moshe warns the spies that appearances can be deceiving- for better and for worse. In so doing we are challenged to improve our essence and ensure that our appearance is always a reflection of our essential good qualities.