Question: Can you please explain the following words from the Katha Upanishad? "The Purusha, no larger than a thumb, the inner Self always dwells in the heart of man. Let a man separate him from the body with perseverance as one separates a tender stalk from a blade of grass."

Babaji:

This again, is an explanation to inspire, so that the mind can lose its thousands and millions of thoughts and get concentrated into one particular thought that is about the Self or the Atma. Instead of trying to look here or there with hundreds and thousands of thoughts, let the mind imagine that I am the Soul, no larger than the thumb. It is only an imagination, not that the Soul is no larger than a thumb or it is larger than a thumb.  Both really make no sense, because the soul is All-Pervading. The Inner Self is always All-Pervading. 

But you imagine when you sit for some sadhana that the Inner Self always dwells in the hearts of man in a particular place, in a particular location, either in between the eyebrows or in the hearts of the people within our physical body. So we shall discriminate this thought first and try to concentrate on that one particular thought.  Our minds become totally interested into that aspect that the soul exists within this body only. Gradually you should practice concentration on that thing. Just like you separate the tender stalk from the blades of grass, and you should separate the rose from amidst the thorns. So instead of the mind going into different parts of the body, different things of the world so it will totally think that "I am this thing, I am this Self, the Atma, sitting in the heart or between the eyebrows," so one will be able to totally concentrate.

But actually as you progress, you would lose all such locations and imaginations when the mind really goes towards the Self because the Self is All-Pervading and it is not hidden in any one particular place.