It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) ordered him "to give one dinar or half a dinar in charity." Miqsam gave its explanation: if he had intercourse with her while the blood was flowing, then one dinar, and if he did so after the blood had stopped but before she took the ritual bath, then he should give half a dinar in charity.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1522