The discussion between Abdullah bin Abbas (may Allah be pleased with him) and Mu'awiyah (may Allah be pleased with him) about touching the corners of the Ka'bah

Abu al-Tufayl narrates that he saw Sayyiduna Mu'awiyah (may Allah be pleased with him) performing tawaf of the Ka'bah, with Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) on his left, and I was walking behind them listening to their conversation. Sayyiduna Mu'awiyah (may Allah be pleased with him) began to touch the two corners on the side of the Hatim (the Iraqi corner and the Syrian corner) as well. So Sayyiduna Ibn Abbas (may Allah be pleased with them both) said to him: "The Messenger of Allah (peace and blessings be upon him) did not touch these two corners." Sayyiduna Mu'awiyah (may Allah be pleased with him) replied: "O Ibn Abbas, no part of the House of Allah is to be abandoned (mahjur)." But Sayyiduna Ibn Abbas (may Allah be pleased with them both) did not let it go, and whenever Sayyiduna Mu'awiyah (may Allah be pleased with him) placed his hand on either of those two corners, Ibn Abbas (may Allah be pleased with them both) said the same thing to him.
This hadith has an authentic chain (sahih al-isnad), but the two Shaykhs did not record it.

Abdullah bin Mulayl al-Ijli narrates: I heard Sayyiduna Ibn Abbas (may Allah be pleased with them both), three days before his death, saying: "O Allah, I repent to You from the fatwas I used to give the people concerning sarf (the exchange of currency)."
This hadith has an authentic chain (sahih al-isnad), and it is among the greatest merits of Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he retracted the one opinion for which, apart from it, nothing else of his was objected to.