“Subhuti, what do you think? Can I be recognized by means of my bodily form?”
“No, Most Honored One, you cannot be recognized by means of your bodily form. Why? Because when you speak of bodily form, it is not a real form, but only an illusion.”
The Buddha then spoke to Subhuti: “All that has a form is illusive and unreal. When you see that all forms are illusive and unreal, then you will begin to perceive your true Buddha nature.”

The Buddha is teaching that the boundaries and labels we put on things are artificial. Our minds create an image of reality and convince us that that self-created image is real on a fundamental level. We say all things are illusory because nothing exists on it’s own. Everything is dependent upon everything else and that’s what we mean when we say things are empty of self nature.