Praise be to Allaah.
As far as a person’s sleeping after praying Fajr is concerned, no text (of Qur’aan or hadeeth) has been reported to indicate that this is prohibited, so the general principle applies (i.e., everything is permitted except that which has been expressly forbidden).
But the practice of the Prophet (peace and blessings of Allaah be upon him) and his Companions after praying Fajr was to remain sitting in the place where they had prayed until the sun rose, as is reported inSaheeh Muslim (1/463) in the hadeeth of Sammaak ibn Harb, who said: “I asked Jaabir ibn Samurah, ‘Did you used to sit with the Messenger of Allaah?’ He said, ‘Yes, frequently. He would not get up from the place where he had prayed Subh until the sun rose. When the sun rose, he would get up. They used to talk about things that had happened during the Jaahiliyyah, and they would laugh and smile.’”
Also, the Prophet (peace and blessings of Allaah be upon him) asked his Lord to bless his ummah in the mornings, as is reported in the hadeeth of Sakhr al-Ghaamidi, who said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “O Allaah, bless my ummah in the mornings.’ Whenever he sent out troops or an army, he would send them at the beginning of the day.’” Sakhr was a trader, and he used to send out his caravans at the beginning of the day, and he did well as a result and made money.”(Reported by Abu Dawood, al-Tirmidhi and Ibn Maajah, with an isnaad in which there is some jahaalah (i.e., one narrator is unknown); corroborating evidence is to be found in a hadeeth narrated by ‘Ali, Ibn ‘Umar, Ibn ‘Abbaas, Ibn Mas’ood and others, may Allaah be pleased with them all.)
For this reason some of the salaf disliked the idea of sleeping after Fajr. Ibn Abi Shaybah reported in hisMusannaf (5/222, no. 25442) with a saheeh isnaad from ‘Urwah ibn al-Zubayr that he said: “Al-Zubayr used to forbid his children to sleep in the morning.” ‘Urwah said: “I do not hear of any man who sleeps in the morning, but I lose interest in that person.”
In summary then, people should make the most of this time which can bring many benefits in this world and in the Hereafter, but if a person sleeps at this time to gain strength to do his work, there is nothing wrong with this, especially if it is not easy for him to sleep at any other time of the day. Ibn Abi Shaybah reported in hisMusannaf (5/223, no. 25454) from the hadeeth of Abu Yazeed al-Madeeni who said: “Umar came to Suhayb one morning and found him sleeping, so he sat down until he woke up. Suhayb said: ‘The Ameer al-Mu’mineen is sitting in his place and Suhayb is sleeping!’ ‘Umar said to him: ‘I did not like to disturb your sleep that could be beneficial for you.’”
As for sleeping after ‘Asr, this is also permitted; there is no saheeh hadeeth from the Prophet (peace and blessings of Allaah be upon him) to indicate that sleeping at this time is prohibited.
As for the words, “Whoever sleeps after ‘Asr and loses his mind as a result has no-one to blame but himself,” which are attributed to the Prophet (peace and blessings of Allaah be upon him), this is a false hadeeth and there is no proof that these words were uttered by the Prophet (peace and blessings of Allaah be upon him).See: Silsilat al-Da’eefah, no. 39.
And Allaah knows best.