Muwatta Malik #746
Hajj
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَكْرَهُ لُبْسَ الْمِنْطَقَةِ لِلْمُحْرِمِ .
Yahya related to me from Malik from Nafi that 'Abdullah ibn 'Umar
used to disapprove of anybody wearing a belt or girdle while in ihram.
About Muwatta Malik
This hadith is #746 from Muwatta Malik, in the Book of Hajj.