A servant is still a servant, and he can tell because the servant was sent with the letter and not the other way around. This servant was sent with a letter and a mountain of silver and gold, and a request for the impossible.
What can he do? Although he can pass laws and order people to do his bidding, there are many things that are still impossible for him, such as making it rain so the farmers’ crops will survive, or winning every war he’s part of, or bringing the dead back to life. He’s heard enough of the impossible to last him into the next life, and he’s nobody’s puppet attached to strings called ‘miracles’.
Someone is trying to pick a fight with him by telling him how useless he really is, sending him false gifts that would become the reason why he’s wrong; why he’s the bad guy for taking gifts without conceding to one ‘little’ request. He wants no part of it, so he tears his clothes to make a point, and is saved from the responsibility of fighting his own battles.