To what extent is it valid to cite the hadith of Ibn 'Abbas in Sahih Muslim as evidence for washing the face and hands after relieving oneself and before sleeping, in imitation of the Prophet, may Allah bless him and grant him peace? And have the scholars mentioned a reason for the Prophet's washing of his face?

The Prophet, peace and blessings be upon him, used to wash his face and hands after his initial awakening from sleep. Scholars mentioned that the wisdom behind this is to prepare for remembrance (dhikr) and to remove drowsiness and the effects of sleep, as narrated by Al-Bukhari (162) and Muslim (278) from Abu Hurayrah, that the Prophet, peace and blessings be upon him, said: "When one of you wakes up from his sleep, he should not dip his hand into the vessel until he has washed it three times, for he does not know where his hand has spent the night."