Musannaf Ibn Abi Shayba 8:2164

Abu Bakr narrated to us, he said: Hafs narrated to us, from Abd al-Malik, who said: I resided in Mecca, and there were Sa’id ibn Jubayr and Ali ibn al-Husayn. Ali ibn al-Husayn performed Tawaf for three weeks, and he prayed two rak'ahs for every week. Then he came to the Stone (al-Hajar) and touched it. And Sa’id ibn Jubayr used to do that during the day.