I'm not sure exactly what documents you want to read (or to refer to and for what purpose).
Below are a few links.
https://www.irs.gov/pub/irs-news/at-03-32.pdf
https://www.irs.gov/taxtopics/tc504
https://turbotax.intuit.com/tax-tips/home-ownership/mortgage-refinance-tax-deductions/L2fzA7hg5
