"I know," Derek replied quietly, sadness creeping into his tone. He combed his fingers through Isaac's hair. "But that's one of the reasons I trust you with Stiles." He knew that there wasn't a single mean bone in the boy's body.
The boy's acceptance pleased him, and knowing that Stiles' training could at least in part be taken care of by Isaac relieved a burden. "And since it is a favor, you may ask something of me as a reward."