Any spiritual retreat other than imperative or founded on the Prophetic practice, is called optional spiritual retreat. One of the things different about this one is that it does not require fasting or a minimum time-span or specific timing, as essential elements. So, if somebody enters a mosque at any time of the day, for any length of time, he can intend seclusion. He will be granted the reward of performing seclusion for as long as he remains in the mosque in that instance. All he needs to do is to intend in his heart and say with his tongue ‘I intend to perform the Sunna of spiritual retreat for the sake of Allah’.