Hello, When trading items with other parties and only Steam Guard is enabled, the trade may be placed on hold for up to 15 days. [2]If the users have been friends for over 1 year, the hold will last 1 day instead.
If Steam Guard Mobile Authenticator has been enabled for both parties for at least 7 days, trades will happen instantly once both sides have confirmed the trade, regardless of friends status.

Thanks for reading.