It is narrated from Sayyiduna Salman al-Farisi (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "When a Muslim meets his Muslim brother and takes his hand, their sins fall away from them just as the leaves fall from a dry tree on a day of violent wind; and even if that is not so, they are both forgiven, even if their sins are like the foam of the sea."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6125