Musnad Ahmad 32:538

Hassan narrated to us, Ibn Lahi'ah narrated to us, Khalid bin Yazid narrated to us, from Sa'id bin Abi Hilal, from Anas bin Malik, that the Messenger of Allah (ﷺ) said: "Indeed, the Children of Israel divided into seventy-one sects; seventy sects perished, and one sect was saved. And indeed, my nation will divide into seventy-two sects; seventy-one sects will perish, and one sect will be saved." They said: "O Messenger of Allah, who are those [in] that sect?" He said: "The Jama'ah, the Jama'ah."