Sunan Abu Dawud
265
Sahih Muquf+2

Ibn ‘Abbas said:If one has intercourse in the beginning of the menses,(one should give) one dinar; in case one has intercourse towards the end of the menses, then half a dinar (should be given)

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