Is it obligatory to wash the hands upon waking up, or is it sufficient to wash them at the beginning of Wudu'?

The jurists have agreed that washing the hands up to the wrists is a Sunnah at the beginning of wudu' (ablution), except for one who wakes up from sleep, regarding whom they differed concerning the ruling on washing them. The majority of scholars hold that it is mustahabb (recommended) and not wajib (obligatory), whereas the Hanbalis are of the view that it is obligatory if one wakes up from night sleep that invalidates wudu', along with the intention and the basmalah (saying "Bismillah"), and that this washing is a separate purification from wudu'. Some scholars have favored the view that washing is obligatory, but the water is not spoiled by dipping the hands into it. The most preponderant view is that washing the hands for one who wakes up from sleep is mustahabb and not wajib, and that dipping the hands into the water does not remove its purity, even if it is said that washing them is obligatory.