While September doesn't need any repayment, Diarmuid has always been taught to help those who help him. It would seem wrong for him not to do at least something little in return for what September has done. It is just how he was raised.

Diarmuid eagerly takes September's hand again when the man reaches for it, "What else do you think I will need, Lord September? Maybe I should make a list of everything. I don't want to forget anything!"