Reference: Fataawa wa Rasaa.il Shaykh ‘Abdur-Razzaaq ‘Afeefee – Page 412, Fatwa No.27
Question: According to the Sunnah, is the time for the qayloolah (siesta) before or after the Zhuhr prayer?
Response: It is before they pray the Zhuhr prayer. [Then], after the [mid-day] heat has lessened, they can pray [the Zhuhr prayer]. And the meaning of his (sal-Allaahu ‘alayhi wa sallam) saying:
«Perform the Zhuhr [prayer] when it is cool», [Saheeh al-Bukhaaree, No.538] is that you should do the qayloolah before [the Zhuhr prayer].
And if he were to sleep after the Zhuhr prayer, then it is not considered as the qayloolah.