https://www.gamespot.com/articles/free-echo-dot-when-you-buy-an-xbox-one-at-amazon-u/1100-6462493/

Microsoft and Amazon are partnering up for a new Xbox One bundle package. Starting October 12, "qualified" Xbox One S and Xbox One S systems purchased through Amazon.com will also come with an Amazon Echo Dot at no extra cost, Microsoft announced. This is the new Amazon Echo Dot, which normally goes for $50 by itself, so this is a pretty nice deal.

This offer is only good "while supplies last," so if you're interested you may want to act quickly. Also note that this deal is good in the United States only.