Throughout the entire letter, it's obvious that Jourdan doesn't fully trust his old master, but he still holds some respect for him. He makes demands to his former master to ensure that his entire family would be safe if he came back down to work for him. I think it's important to point this line out in the letter because Jourdan is explicitly saying that he has legal documentation stating that he is free. He is making sure that his old master knows that he can't trap him into becoming a slave again if he were to go back down. I think that he did a good job in conveying in his letter how free he was and how much he and his family have been able to grow due to it.