It was narrated from Ibn 'Abbas that the Messenger of Allah (ﷺ) said: 'When anyone of you swears an oath, let him not say: 'What Allah wills and what you will.' Rather let him say: 'What Allah wills and then what you will.'
It was narrated from Hudhaifah bin Yaman that : a Muslim man saw in a dream that he met a man from among the People of the Book, who said: What good people you would be if only you were not committing Shirk. For you say: 'What Allah wills and Muhammad wills. ' He mentioned that to the Prophet (ﷺ) and he said: By Allah, I am aware of that. Say: 'What Allah wills then what Muhammad wills. 'Another chain from Tufail bin Sakhbarah, the brother of 'Aishah by her mother, from the Prophet (ﷺ), with similar wording.