In high-school and college, I vastly preferred explaining homework solutions to other people than doing my own homework.
The knowledge I guard from others is the knowledge I am (or will be) obligated to protect by contract.
Knowledge belongs to the person who knows. This is simply tautology.
I don't know if sharing knowledge is showing someone my soul. But perhaps the enthusiasm with some knowledge is shared is.
I would hide knowledge if I were required to by IP laws.
I gained knowledge in various ways, including: experience, thought, guided experiment, practice, insight, reading, observing, clarifying, and yes by teaching also.