In the name of Allah,
Narrated Abu Huraira:
Allah’s Messenger (ﷺ) said, “If anyone of you performs ablution he should put water in his nose and then blow it out and whoever cleans his private parts with stones should do so with odd numbers. And whoever wakes up from his sleep should wash his hands before putting them in the water for ablution, because nobody knows where his hands were during sleep.”[I]. Click here for commentary on this Hadith.
The scholars differed as to whether this washing of the hands upon awakening from sleep is wajib (obligatory) or mustahabb (commendable or recommended). Noble scholars also disagree on whether this washing applies upon waking from night sleep or any time of the day.
The Imams, Ahmad, and Daawood adh-Dhaahiree stipulated that it be legislated only after rising from a night’s sleep. They believed this injunction was about night-time sleep since بَاتَتْ يَدُهُ (spending the night)[ii]. This is corroborated by another hadith of Tirmidhi, which states, “…no one knows where his hand was during the night.” “If anyone awakens from the night.’[iii]
Others say it’s recommended, not mandatory. Many scholars, including ‘Ataa’, Maalik, Al-Awzaa’i, Ash-Shaafi’i, Ishaaq, and the Hanafi scholars, agreed with this point of view.
Imam Ash Sha’fi said: I would like for each person who wakes up from sleep be it daytime sleep or otherwise, not to dip his hand into the water until he washes it. If he dips his hand before washing it, this will not spoil the water, unless there is some najasah on his hand, though I would hate for him to do so.’[iv]
In case of doubt about najis, it is makrooh to immerse hands in water without washing them after waking up. If you are sure that your hands are najis, it is forbidden. If you are sure that your hands are free of najasah, it is sunnah to wash them before immersing them in water.
Allah Knows Best.
Sources:
[i] Bukhari 162
[ii] Tayseer al-Allaam Sharh Umdatul-Ahkaam by Shaykh Abdullah ibn Abdur – Rahmaan Aal Bassaam. Page 12
[iii] Jami` at-Tirmidhi 24, sahih Albani
[iv] Fiqh Al Ibadat Jurisprudence of worship According to the Shaafi school of Thought by Hajjah Durriya al Aytah, page 47