Musnad Ahmad 25:913

Husayn ibn Muhammad narrated to us, Yazid—meaning Ibn ‘Ata’—narrated to us, from Yazid—meaning Ibn Abi Ziyad—from ‘Ikrimah, from Ibn ‘Abbas, who said: "The Prophet, may Allah bless him and grant him peace, came while he was suffering from an ailment, so he performed Tawaf around the House on a camel, and with him was a curved staff. Every time he passed by it [the Black Stone], he touched it with the staff. When he finished his Tawaf, he made the camel kneel and prayed two rak'ahs."