Musnad Ahmad 27:15

Hashim narrated to us, 'Ata' ibn al-Sa'ib informed us, from 'Abdullah ibn 'Ubayd ibn 'Umayr, that he heard his father say to Ibn 'Umar: "Why do I not see you touching except these two corners: the Black Stone and the Yemeni Corner?" Ibn 'Umar said: "If I do so, it is because I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'Indeed, touching them removes sins.'" He said: "And I heard him say: 'Whoever performs a circuit (tawaf) of seven rounds, counting them, and prays two rak'ahs, it is for him like the freeing of a slave.'" He said: "And I heard him say: 'A man does not lift a foot nor place it down except that ten good deeds are written for him, ten evil deeds are removed from him, and ten degrees are raised for him.'"