Do Sikhs believe in the concept of a human soul/spirit beyond just body and mind? If so, where does this soul reside? Inside the man? Outside?
As per Gurbani, there is only one thing which exists in reality, everything else is an illusion. The only real thing is called God or soul. The soul is indivisible, formless, perfect and unchanging. Therefore, it would be wrong to assume that every person has a separate soul. The question: "whether the soul lives inside or outside a person?" is also flawed. The concept of inside/outside in something which is formless does not make sense. Also, you need more than one thing for inside/outside to make any sense. The one soul is everything, and it permeates everything. Mind is an illusion created out of soul. Mind is individualistic. Mind is the basis of ego. Body and the universe is a temporary perception created by the mind.
If we must think in terms of duality from the perspective of an individual man and must decide whether the soul is inside or outside this man. I suggest the following analogy: Carve a jug from a block of ice, and then drop this jug in ocean. The jug represents man and water represents soul. Water is inside the jug, outside the jug, and the jug is made of water. This jug is temporary and as soon as it loses its hardness (ego), it will dissolve and disappear into water.
The following excerpts from personal notes of Sant Isher Singh ji Rarewale may help further. These notes were published after Sant ji passed away:
Chapter 1: "Yesterday was August 5, 1965. This perishable, ever changing and pain-prone body completed its fifty eight years of existence and started the fifty ninth year. But I am a soul. I have no birth, no death, and I do not age. Till the day I was ignorant and thought I was a body, I suffered immensely and my mind had no peace. I mistakenly thought that I was somebody who was subject to birth and death. With the Guru’s grace I realized my true existence. From that day onwards, I am no longer a prisoner in this body. I have been living in bliss in a realm which is above birth and death and which is above this perishable body. Peace and turmoil are both qualities of mind -- soul is a witness to both of these. It’s like there are two images painted on a canvas: one is a horse in gallop and the other one a horse standing still. The canvass is a witness to both. Like the two images of horses, turmoil and stillness are the qualities of the mind. As the canvas has nothing to do with what goes on with the images, so the soul remains forever still and aloof from mind."
Chapter 21: "Our mind has conjured an illusion which has been called many things such as: maya , avidya , magic, or ignorance. It is similar to water appearing in a mirage. Everything invisible/visible in this creation from Brahma to a blade of grass is no more than a figment of imagination. Names and forms are nothing more than imaginary symbols or ideas in our mind. Everything seen, heard, felt or spoken is definitely an illusion. Use this knowledge as water for daily bathing of your mind. Maintain the memory of the Lord always in your mind. The Lord, who is beyond form and attributes, is indivisible, complete and perfect. With practice over time, the mind will start merging into the vast consciousness and will start experiencing the absolute meditation. Steady increase of this practice will quieten the mind and will lead to the bliss of salvation-while-alive, and will result in formless salvation once the body has run out its pre-ordained time.
ਬੰਦੇ ਖੋਜੁ ਦਿਲ ਹਰ ਰੋਜ ਨਾ ਫਿਰੁ ਪਰੇਸਾਨੀ ਮਾਹਿ ॥ ਇਹ ਜੁ ਦੁਨੀਆ ਸਿਹਰੁ ਮੇਲਾ ਦਸਤਗੀਰੀ ਨਾਹਿ ॥ O human being, search your own heart every day, and do not wander around in confusion. This world is just a magic-show; no one will be holding your hand. (SGGS 727)
ਕਬੀਰ ਮਾਇਆ ਡੋਲਨੀ ਪਵਨੁ ਝਕੋਲਨਹਾਰੁ ॥ ਸੰਤਹੁ ਮਾਖਨੁ ਖਾਇਆ ਛਾਛਿ ਪੀਐ ਸੰਸਾਰੁ ॥ Kabeer, Maya is the butter-churn, and the breath is the churning-stick. The saints eat the butter, while the world drinks the whey. (SGGS 1365)"
Waheguru ji ka Khalsa, Waheguru ji ki Fateh