You will want to “Credit” your commission, at closing, and not use the word “gift.” Typically, a gift is something that the lender would need to document as part of the loan process.
You will need to have escrow instructions, signed by the seller, stating that you intend to credit $xx to the buyer for closing costs.
Notify title of the amount and what it’s for so that they can include it on the Closing Disclosure.