Musnad Abu Ya'la al-Mawsili 154:147

Abu Khaythama narrated to us, Rawh ibn ‘Ubadah narrated to us, al-Awza‘i narrated to us, from al-Muttalib ibn ‘Abd Allah ibn Hantab, who said: Ibn ‘Umar used to perform ablution three times [for each limb], attributing it to the Prophet, may Allah bless him and grant him peace. And Ibn ‘Abbas used to perform ablution once [for each limb], attributing it to the Prophet, may Allah bless him and grant him peace.