But why should you do that?
What is moral about not killing your friend and taking their stuff?
You could get a lot of stuff that way.
As I said, you do not understand this and at the age of 61, I'm not sure I have enough time to explain it to you. It is true, one can get a lot of stuff by killing a friend, but this kind of behavior is rather rare among humans.
To put it in the simplest terms, moral codes exist in human society, so that humans can live in close proximity to one another and cooperate.
Moral codes exist for many reasons but these two statements contradict one another.
If problems are rare why are "codes" needed?
And is your reason you do not take your friends stuff because you adhere to some code? If we took away the code you would have no problem?
No, you are quite wrong. Moral codes exist for the reason I gave. There is no other reason for them.
I can see you are having trouble with this concept, and I blame the industrial age. Life is simply too easy for you. You've caught me at a good time, and I'll give it a try. I'm probably wasting my time, but I am a river to my people, and as with any river, most of the water goes by without notice.
Try this: Take a look around and consider everything you can see that was somehow touched by a human hand, other than yours. This will be practically everything in your home. It has to go. You have to leave your home, which was constructed by humans, and go to someplace where there are no humans, and nothing touched by humans. There are still a few places like this. You are now naked and alone, and soon you will be hungry. If you are fortunate, there maybe some edible plants nearby, and some fresh water. Help yourself to as much as you need. In any case, you are probably going to die of either thirst, starvation, or exposure. Humans do not function well when left alone. Your teeth are flat, your claws are soft, you don't climb very well, and any other animal in the forest can run faster than you, which means you can't catch the ones you want to eat, and you can't outrun the ones which want to eat you.
You need help. You need other people. In order for you to have any friends, you'll need to behave in way which makes you useful to have around. You need a moral code. The first rule is don't kill your friends. You can't keep a group together if one person can kill another one at any time. No one would dare go to sleep while someone else is around. When everyone sees the value of not killing friends, everyone can sleep well.
The second rule is don't steal your friends stuff. Within the obvious limits, humans are the only animals who collect stuff for future use. This includes food and most importantly, tools. Once again, the problem is falling asleep. When everyone sees the value of keeping their hands off other people's stuff, everyone can sleep with the confidence of waking up alive, with all your stuff.
The person who follows these rules is allowed to stay in the group, which greatly reduces the odds of dying of thirst or starvation. The harsher the environment, the more critical it is to live in a group. A person who kills and steals will be driven out and forced to live alone. That is a death sentence, if they don't all get together and decide to kill you.
Adhering to a moral code is at its roots, a selfish act of self preservation. You may think the particular details of your moral code make you a better person, but they don't. You are just doing your best to survive.