(a) Sayyiduna Adi bin Hatim (may Allah be pleased with him) says that a man gave a sermon in the presence of the Prophet (peace and blessings be upon him) and said: Whoever obeys Allah and the Messenger will be rightly guided, and whoever disobeys them both has gone astray. The Messenger of Allah (peace and blessings be upon him) said: "You are a bad speaker; say it like this: Whoever disobeys Allah and the Messenger has gone astray."
(b) These are the words of Waki's hadith, but al-Adani did not mention this statement: "Say: And whoever disobeys Allah and His Messenger has certainly gone astray."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5809