Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. To proceed:
This expression should not be said, because it implies objecting to what Allah تعالى has decreed and ordained. Allah سبحانه وتعالى knows best the circumstances of His servants, and He possesses profound wisdom in what He decrees for them of health and illness, wealth and poverty, and all other circumstances.
What is prescribed when visiting a sick person or hearing of his illness is to supplicate for him with good words, such as: “May Allah grant him well-being,” “May Allah cure him,” and similar expressions.
And Allah تعالى knows best.