Know surely, beyond doubt, that ones belief and Islam is invalid and ones good deeds are not acceptable lest one utters the two testifications:
أشهد أن لا إله إلَّا الله
وأشهد أنّ محمَّدًا رسول الله
I testify no one is God except Allah and I testify Muhammad is the Messenger of Allah. It is not a condition to say these exact terms, rather it is sufficient to say what gives the same meaning, such as saying:
“There is no lord but Allah”
لا ربَّ إلَّا الله
(la rabba illallah),
“Muhammad is the Messenger ofAllah”
محمَّد نبيّ الله
(Muhammad nabiyyullah).
Likewise if one utters what has the same meaning even in other than the Arabic language. For the validity of ones Islam; this utterance suffices if done once in a lifetime; this is for the person who was not a Muslim and wanted to embrace Islam. After this one time, the utterance is obligatory in every prayer for the validity of the prayer.