Sleeping for the Health
The best time to go to sleep is after food has been digested. It is wise to start off sleeping on the right side, just as the Prophet, may Allah bless him and grant him peace, used to do. This was confirmed by 'Ayesha when she said, "He, may Allah bless him and grant him peace, used to go to sleep starting on his right side, and facing Makka.
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Sleep during the day is bad. It affects the complexion, gives rise to discases, and makės a man lazy. It should be avoided, except during the mid-day heat, in accordance with the hadith of the Prophet, may Allah bless him and grant him peace, "Have some sleep, for the shayatin never sleep." And again, he said, "Make it easier for you to rise for prayer during the night by having a short sleep during the day. " He also said, "Sleeping during the morning hinders provision."
It has been related by Jabir that the Prophet, may Allah bless him and grant him peace, forbade a man to sleep partly in the sun and partly in the shade. Among the ahadith it is also related that he forbade a man to sit partly in the sun and partly in the shade. These are the statements of al-Hafiz Abu Nu'aim. Abu Daw'ud has related the same in his book called As-Sunan.
Ayesha, may Allah be pleased with her, said, "Whoever goes to sleep during the late afternoon will make himself go mad - and he only has himself to blame." Al-Imam said, There is one thing that is forbidden for a man, and that is to sleep during the late afternoon, lest he lose his wits." Sleep is also forbidden after the dawn prayer until the sun has risen, and before the night prayer. The Prophet, may Allah bless him and grant him peace, disliked sleep before these two times as much as he disliked talking after them, although if such talk was about wisdom, or about Allah, or farming, then it was not disliked by him.
Sleeping face down is also forbidden, because such sleep is the sleep of the Fire.
Finally, it is better to go to sleep in wudu, as has already been stated in the hadith concerning purity.