Abu Dawud Book 1, Hadith Number 212.

Chapter : On mutual contract and eating with a menstruating woman.

Narated By Abdullah ibn Sa’d al-Ansari : Abdullah asked the Apostle of Allah (PBUH): What is lawful for me to do with my wife when she is menstruating? He replied: What is above the waist-wrapper is lawful for you.

The narrator also mentioned (the lawfulness of) eating with a woman in menstruation, and he transmitted the tradition in full.