Contract for loan from parent?

[Shalen Takaaze]

If I am going to borrow funds from a parent to add to my own initial investment for downpayment and rehab costs, should I get a written legal contract? For context, I already have possession of the money and I am letting it fully season for two months so that the underwriters don't question the deposit. This was one of the options given to me by my mortgage lender and the option that was chosen by the parent I am borrowing the money from. Would appreciate any advice. Thank you!