In sleep your spirit rises to travel about and observe the world.
You fall into a deep sleep while your spirit leaves your body invisibly in incorporeal form and travels to distant locations. Your spirit can move 100 feet per round, and can see and hear anything you could if you were in the same location. The spirit can be blocked by any spell that wards incorporeal creatures, and it can be detected and attacked in the same way as incorporeal creatures can. Your spirit can do nothing but move and observe—it cannot speak, attack, cast spells, or perform any other action.
At the end of the spell, your spirit instantaneously returns to your body and you wake up. If your body is disturbed or attacked while your spirit is wandering, the spell ends immediately.
Source: Spell Compendium, page 74. Previously published in Heroes of Horror, page 128, and in Complete Divine, page 164.