مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2195
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn Abbas(رضي الله عنه) that The Messenger of Allah (ﷺ) said: "Let him give a dinar, or if he cannot afford that, then half a dinar," meaning the one who had intercourse with his wife when she was menstruating.
Musnad Ahmad 2201Saheeh mawqoof; this is a very weak (da'eef jiddan) isnad]