I think he is explaining the concept. So the reference: The concept is reflected in the Quran, Surah Al-Baqarah (2:201): “And of them there are some who say: ‘Our Lord! Give us in this world that which is good and in the Hereafter that which is good, and save us from the torment of the Fire!’” And in Hadith, such as: “The world is the believer’s prison and the disbeliever’s paradise.” (Sahih Muslim) Another related Hadith is: “The intelligent person is one who subdues his self and works for what is after death, and the foolish person is the one who follows his desires and places hope in Allah.” (Tirmidhi) These teachings emphasize that our actions in this world are preparatory for the rewards and consequences in the Hereafter.