Does the prayer become invalid if the worshiper says "Hass" – meaning "My Lord is sufficient for me" – when raising his head from prostration and before the takbir, if he suffers from whisperings (waswasah) in the form of hearing words that displease Allah?

The prayer is not invalidated by unintentional speech. This is the view of the majority of scholars. It is prescribed for one who speaks unintentionally to perform the prostration of forgetfulness (sujud al-sahw) after the salutation, if praying alone. If the worshiper omits the prostration of forgetfulness, their prayer is still valid. If praying behind an Imam, the Imam bears the burden of the forgetfulness on behalf of the congregant.