All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
He who intends to fast then sleeps the whole day, his fasting is correct and he does not have to make this day up. To the contrary, a person who becomes unconscious the whole day and does not regain consciousness until after sunset, his fasting is not correct. What the questioner has stated as a quotation from Shaykh 'Ajeel An-Nashmi, may Allaah have mercy upon him, is in relation to a person who became unconscious and not someone who slept the whole day. We draw the attention of the questioner that a Muslim has to perform the five daily prayers at their fixed time. Allaah says (interpretation of meaning): {Guard strictly the prayers (five obligatory) especially the middle prayer (i.e. 'Asr). And stand before Allaah with obedience [and do not speak to others during the prayers].}[2:238]. Whoever wants to sleep has to take the necessary measures in order to wake up and perform the prayers at their fixed time, yet if he does not wake up because he was overcome by sleep, we hope that there is no harm on him as the Prophet said : "There is no remissness in sleeping." [Muslim] But this does not apply to someone who makes this a habit, sleeps and fails to perform most of the prayers and does not take the necessary means to wake up. A Muslim has to perform the prayers at their fixed time and sleeping does not make combining prayers permissible. In addition to this, too much sleeping mainly during a day of fasting, is a reason for missing many great acts of worship like reading the Qur'aan. This blessed month is not a month of sleeping but a month of worship and remembrance, so a wise person should use its time in performing acts of worship and not sleeping.
Allaah knows best.