al-Qurtubee said, “The scholars said there is no night and day in Paradise, rather they will be in eternal everlasting light. They will know when night comes because curtains or screens will be put up and doors will be closed, and they will know when day comes because the curtains or screens will be taken down and the doors will be opened. This was mentioned by Abul-Faraj ibn al-Jawzee” [al-Qurtubee, at-Tadhkirah, p. 504]

Ibn Katheer in his commentary on the aayah: “And they will have therein their sustenance, morning and evening. Such is the Paradise, which We shall give as an inheritance to those of Our slave who have been al-Muttaqoon [pious and righteous]” [19:62-63] said, “This means something approximate to the times of day and night, it does not mean that there will be a day and night there. They will know the passing of time by the changes in the light” [Tafseer Ibn Katheer, 4/471]

On the same subject, Ibn Taymiyyah said, “There is no sun and moon in Paradise, and no day or night, but they will know morning and evening from a light that shines from the direction of the Throne” [Majmu’ Fataawa Shaikh al-Islaam, 4/312]