Sunan Abu Dawud
2169
Sahih Muquf+3

Narrated Abdullah ibn Abbas: If a man has sexual intercourse (with menstruating woman) during her bleeding, he should give one dinar as sadaqah, and if he does so when bleeding has stopped, he should give half a dinar as sadaqah

Sahih MuqufAl-Albani
Sahih MuqufMuhammad Muhyi Al-Din Abdul Hamid