A spot of blood appearing at a small wound without spreading does not meet the Hanafi rule for flowing blood. If it moves beyond the wound to an area that falls under the cleansing rule, wudu is invalidated.
The key distinction is the manner of emergence, not merely the visual presence of redness.
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Invalidators of Wudu: Actual and Constructive Causes
A spot of blood appearing at a small wound without spreading does not meet the Hanafi rule for flowing blood. If it moves beyond the wound to an area that falls under the cleansing rule, wudu is invalidated.
The key distinction is the manner of emergence, not merely the visual presence of redness.