It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that during the days of Mina the Messenger of Allah (peace and blessings be upon him) sent out a crier who was calling out: "Do not fast on these days, for they are days of eating, drinking and bi'al." And al-bi'al means intimacy with women.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11537