“You’re my friend, but I can’t let you know that I killed your father, because you might tell that to someone else and that would be unpleasant for me.”
“If there’s even a small chance that letting you know will reduce my ability, down the line, to save the world, then I am physically incapable of letting you know.”
If the Vow prevented him from letting Draco know on a permanent basis for this reason, it would prevent him from telling him with the intention of obliviating him afterwards, since there would be a chance he would get away without being obliviated.
“If there’s even a small chance that letting you know will reduce my ability, down the line, to save the world, then I am physically incapable of letting you know.”
If the Vow prevented him from letting Draco know on a permanent basis for this reason, it would prevent him from telling him with the intention of obliviating him afterwards, since there would be a chance he would get away without being obliviated.
Good point. He’s counting on Minerva to obliviate Draco, which makes it a bit safer.