It is narrated from Sayyiduna al-Harith bin Hisham (may Allah be pleased with him) that he said: "O Messenger of Allah (peace and blessings be upon him)! Tell me of something to which I may hold fast." He (peace and blessings be upon him) said: "Keep this under your control," and he (peace and blessings be upon him) pointed to his tongue.
Hadith Referenceالمعجم الأوسط / باب الألف / 1915
Hadith Takhrij«أخرجه الطبراني فى «الكبير» برقم: 3348، 3349»