Rewatching this episode, I realized something.
This is the first time Sam hears Mary’s voice.
In his head, he’s imagined it-any and all family video tapes having been destroyed in the fire-he’s tried to see if he could remember it, but this is really the first time he hears his mothers voice. The first time in twenty-three years. The first time he can hear it.
The first (and last) time she says his name.