Leviticus 15:25
And if a woman have an issue of her blood many days out of the time of her separation, or if it run beyond the time of her separation; all the days of the issue of her uncleanness shall be as the days of her separation: she shall be unclean.
Cross-reference
Leviticus 15:19-24 provide the baseline rules for regular menstruation, which 15:25 extends to abnormal discharge — same impurity laws.
Leviticus 12:4 addresses postpartum uncleanness — another blood-related impurity, though with different duration and rules.
Matthew 9:20 describes a woman with a 12-year discharge of blood, exactly the condition here — illustrating the OT law in a NT healing.
Mark 5:25 also recounts the same woman with a 12-year discharge, providing another NT witness to this condition.
Luke 8:43 likewise describes the woman with an issue of blood, confirming the NT usage of this Levitical condition.
Mark 7:20-23 contrasts ceremonial uncleanness by teaching that defilement comes from within, not from external discharges like this.