Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates from his father that when Umar bin al-Khattab (may Allah be pleased with him) accepted Islam, the Messenger of Allah (peace and blessings be upon him) struck his chest with his hand three times, saying: "O Allah, remove whatever rancour is in his chest and give him faith in its place." He (peace and blessings be upon him) said this three times.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13134