(a) It is narrated from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) (the narrator thinking it was from him) that the Prophet (peace and blessings be upon him) ordered him to give two-fifths of a dinar in charity. There is disagreement in its chain and its text.
(b) Al-Awza'i, with this same chain, narrates from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) that he had a wife who disliked men. Whenever he wanted her, she would excuse herself with menstruation, and he thought she was lying. He came to her and found that she was telling the truth. Then he came to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) ordered him "to give two-fifths of a dinar in charity."
It is munqati' (broken) between Abd al-Hamid and Umar.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1518