Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 902
Narated By Abdullah ibn Umar : Sa'id ibn Ziyad ibn Subayh al-Hanafi said: I prayed by the side of Ibn Umar and I put my hands on my waist. When he finished his prayer, He said: This is a cross in prayer; the Apostle of Allah (pbuh) used to forbid it.