Abdullah bin Ubayd bin Umayr narrated: A man said to Ibn Umar (may Allah be pleased with them both): O Abu Abd al-Rahman, why is it that I see you touching (istilam) these two corners and never leaving them? And Ibn Umar (may Allah be pleased with them both) used to do so. He said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Touching these two sheds sins away."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13389