Is it obligatory to utter the Two Testimonies as a precaution to renew one's faith, or is what is recited in prayer sufficient?

It was not the custom of the righteous predecessors to be afflicted by obsessive doubts (waswasah) concerning matters of faith and the pronouncement of the two Shahadas because of such doubts. Nor should a Muslim open the door to obsessive doubts for himself, due to their immense harm and grave danger, especially when they relate to matters of Tawhid (monotheism) and faith. A Muslim should not pay attention to these obsessive doubts, and he should instead increase in the remembrance of Allah and the pronouncement of the two Shahadas as an act of worship to Allah and remembrance of Him, not out of doubt in his faith or to renew it after apostasy or disbelief.