(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
It is narrated from Sayyiduna Hudhayfah (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Do not say: 'Whatever Allah wills and so-and-so wills,' but rather say: 'Whatever Allah wills, then whatever so-and-so wills.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5810
Abdullah bin Yasar (may Allah have mercy on him) narrates from Qutaylah bint Sayfi al-Juhaniyyah (may Allah be pleased with her) that a Jewish scholar came to the Prophet (peace and blessings be upon him) and said: O Muhammad! You would be excellent people were it not that you associate partners (with Allah). He (peace and blessings be upon him) said: "'Subhan Allah' (Glory be to Allah)! How is that?" He said: When you swear an oath, you say: By the Ka'bah. The Prophet (peace and blessings be upon him) paused, then said: "Whoever swears an oath, let him swear by the Lord of the Ka'bah." Then he said: You would be excellent people were it not that you say: Whatever Allah wills and so-and-so wills. The Prophet (peace and blessings be upon him) paused for a little while, then said: "Whoever says: 'Whatever Allah wills,' then let him say after a pause: 'then whatever you will.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5811
Ibn Abbas (may Allah be pleased with them both) says: A man came to the Messenger of Allah (peace and blessings be upon him) and spoke with him about some matters, and the man said to the Messenger of Allah (peace and blessings be upon him): Whatever Allah wills and you (will). The Prophet (peace and blessings be upon him) said: "Have you made me equal to Allah? Say: Whatever Allah alone wills."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5812