For washing to occur, water must reach the limb so that the act truly qualifies as washing. Simply passing a wet hand is not washing.
The commentary describes the minimum flow of water, even if a drop or two runs. Hence washed limbs require actual washing, not merely wiping.
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What Counts as Washing
Taharah and Wudu Obligations: Limits, Evidence and Juristic Differences
For washing to occur, water must reach the limb so that the act truly qualifies as washing. Simply passing a wet hand is not washing.
The commentary describes the minimum flow of water, even if a drop or two runs. Hence washed limbs require actual washing, not merely wiping.