نَوْمُ أَوَّلِ النَّهَارِ خُرْقٌ، وَأَوْسَطُهُ خُلْقٌ، وَآخِرُهُ حُمْقٌ
[Bukhari – Book of Manners #1242]
Imâm Bukhari رحمه الله said:
As for the hadith, “Whoever sleeps after ‘Asr and loses his mind as a result has no-one to blame but himself,” then it is a weak [narration] and it is known for its weakness.
The Sheikh رحمه الله comments on this narration in his explanation of al-Adab al-Mufrad by Imâm Bukhari on page 363 Vol. 3. He رحمه الله said,
This narration contains beneficial guidance that relates to mankind’s daily and nightly life and conduct. [This guidance] is pertaining to the time of sleeping/napping, and the origin of the time to sleep is during the night.