Buyer reimbursement for expenses

[Santosh Prabakar]

I had my house under contract in TX but the buyer backed out during signing. I have spent around $6k to fix few things that the buyer wanted. 

The buyer is willing to reimburse the expenses so that I dont take him to the court. What documents do I make him sign to make it official that he is agreeing to reimburse and not change his stand later?