One cannot say that he knows Jesus if he does not obey him. When Jesus was informed that his mother and siblings were looking for him, He asked "who is my mother and bother,......you who obey my words and keep it".

Its very simple. Even in our earthly life, we cant say we are close to our mother or father except if we truely obey them. Jesus said, whoever will enter into my kingdom will be like one of these childre. This is because children carry out instructions more willingly than we adults.

I dont think its really a new commandment. This is because in the old testament, the children of Isreal would have been close to God if they had obeyed him.