Does one who, in a fit of rage, declared, "I do not bear witness that there is no god but Allah, and I do not bear witness that Muhammad is the Messenger of Allah," need to perform ghusl and renew their Shahada, given that they do not recall if they were a child or an adult at the time?

This statement is an act of disbelief (kufr), but scholars have differed regarding the apostasy of a child. If the one who uttered it then repented, Allah will accept their repentance. The general rule is that if an apostate pronounces the two Shahadas or prays, they are considered Muslim. Scholars have differed regarding the obligation of ghusl (ritual bath) for an apostate or an original disbeliever upon embracing Islam. We advise the questioner to turn away from contemplating this incident and to strive in obedience to Allah.