Abu al-Darda (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Whoever is given gentleness has been given a share of goodness. And whoever is deprived of his share of gentleness has been deprived of his share of goodness as well." And he said: "The heaviest thing in the scale of the believer is good character, and Allah Almighty dislikes foul speech and obscene talk."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20798