the view of most jurists.

As for the wisdom behind washing the hand, there are three views:

The first is that there is a fear of impurity being on the hand—for example, if it passes over the area cleansed by dry wiping after relieving oneself while that area is damp with perspiration, or over some dung, or the like.

The second is that it is an act of worship whose rationale cannot be discerned.

The third is that it is because the hand spends the night in contact with Satan. As reported in the two Sahīh collections, Abū Hurayrah narrated that the Prophet, peace and blessings be upon him, said:

“When one of you wakes from sleep, let him draw water into his nostrils, for Satan spends the night inside his nose.”

He thus commanded washing, explaining it by Satan’s spending the night inside the nose. This shows that this is a reason for washing away impurity. The hadith is well known.

His statement,

“For none of you knows where his hand has spent the night,”

may refer to this. This would therefore be one of the operative causes whose relevance is attested by the revealed text. Allah knows best.