Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) climbed Safa, took hold of his tongue and said: "O tongue! Speak good and you will gain, and keep silent from evil and you will be safe, before you come to regret." Then he said: I heard the Messenger of Allah (peace and blessings be upon him) saying: "Most of the sins of the son of Adam are due to his tongue."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10408