When someone wishes to convert to Islam as their religion, reciting the Shahadah marks their entrance into Islam and their life as a Muslim.
أَشْهَدُ أَنْ لَا إِلَٰهَ إِلَّا ٱللَّٰهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا رَسُولُ ٱللَّٰهِ
“Ash-hadu alla ilaha illa-Allah wa ash-hadu anna Muhammadan rasul-Allah”.
“I bear witness that there is no deity (none worthy of worship) but Allah, and I bear witness that Muhammad is the Messenger of Allah.”