Nafi' (may Allah have mercy on him) said that Ibn Umar (may Allah be pleased with them both) used to be cupped while fasting; later he gave that up and used to be cupped at night. I do not know whether it was because of something he remembered or something he heard.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8304