Prohibition of heresies in religion

السلام عليكم
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيمِ
Jabir (May Allah be pleased with him) reported: Whenever the Messenger of Allah (PBUH) delivered a Khutbah, his eyes would become red, his tone loud and he showed anger as if he were warning us against an army. He (PBUH) would say, "The enemy is about to attack you in the morning and the enemy is advancing against you in the evening". He would further say, "I am sent with the final Hour like these two fingers of mine.'' Messenger of Allah (PBUH) held up his index finger and the middle finger together to illustrate. He used to add: "To proceed, the best speech is the Book of Allah and the best guidance is the guidance of Muhammad (PBUH), the worst practice is the introduction of new practices in Islam and every Bid`ah is a misguidance". He would also say, "I am, in respect of rights, nearer to every believer than his own self. He who leaves an estate, it belongs to his heirs, and he who leaves a debt, it is my responsibility to pay it off.'' [Muslim].

(Source: Riyad-Us-Saliheen Pg 178 hadith 170)