Authentic Supplication Number 129.

The Messenger of Allah  said to ‘Asma’ binti ‘Umaysin: “Shall I not teach you a few words which you can say when you are distressed – or at the time of distress – Allahu, ‘allahu rabbee la ‘ushriku bihi shay’an (150).

Footnotes.
(150) Allah, Allah my Lord I associate not with Him a thing.

Reporters.
Ibn Taymiyah referenced this hadeeth to Abu Dawood, and Al-Albani said it was a comely hadeeth. The hadeeth, he said, has an unknown person in its chain, yet, the hadeeth has testimonial in the hadeeth of `Aishata reported as #2369 by Ibn Hibban in his Saheeh which includes that the phrase be repeated twice. Al-Albani included this hadeeth in The Authentic of Good Sayings as #100.