One day a non-Jew sought to find out what the whole Torah was all about. He went to many prominent rabbis of his time and said to each one: “Look, I don’t have much time. Can you tell me quickly what the Torah is all about?”
According to the tale, he wanted to know in as short a period as he was able to stand on one foot. Each rabbi sent him away and the man became increasingly intent on an answer to his question.
Finally, he met one rabbi that told him, “The most basic law is: Love thy neighbor as thyself. The rest is commentary. Go and learn.”
There we have the most fundamental of the 613 laws (ethical and ritual) and it relates to our involvement with one another (between one human being and another). This is because the physical plane is the crucial one in our existence.
Therefore, “Love thy neighbor as thyself” is the most basic law in Judaism.