Sayyiduna Ibn Abbas (may Allah be pleased with them both) said regarding the saying of Allah Almighty, "So keep away from women during menstruation" [Surah al-Baqarah: 222]: Keep away from intercourse with their private parts. And regarding "And do not approach them until they become pure" [Surah al-Baqarah: 222], he said: When they have become pure from the blood and have thoroughly purified themselves with water. Then regarding "Then come to them from where Allah has commanded you" [Surah al-Baqarah: 222], he said: In the private part, and do not go beyond it to anything else; whoever does anything (other than that) has transgressed the limit.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1481