Maliks Muwatta Book 20, Hadith Number 216.
Section : Doing the Prayer at al-Muarras and al-Muhassab.
Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to pray dhuhr, asr, maghrib and isha at al-Muhassab, and then enter Makka at night and do tawaf of the House.