Sunan Ibn Majah
3882
Sahih+3

It was narrated that Asma’ bint ‘Umais said:“The Messenger of Allah (ﷺ) taught me some words to say at times of distress: Allah! Allahu Rabbi la ushriku bihi shay’an (Allah, Allah is my Lord, I do not associate anything with Him).”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi