In 'Sonic Adventure 2', Shadow made Amy a promise, what was the promise made?

(HINT) Shadow remembered that revenge was not what Maria Robotnik wanted before she died thanks to Amy. Shadow đã đưa ý kiến to Amy, ''I'v got to go now! I have to keep my promise to Maria and you.'' Before this though Amy đã đưa ý kiến something to Shadow like, ''PLEASE SAVE THE HUMANS SHADOW! I BEG OF YOU! GIVE THEM A CHANCE!