When. In karb — the kind of trouble that constricts: bad news, a night in a hospital corridor, a situation with no next step. It is said at the moment it strikes, and repeated.
The words. There is no request in it. Three statements of la ilaha illallah, each completed differently, and then it stops. A person in distress is not asked to formulate what he wants; he is given something to say that is true regardless of what happens next.
Al-Azim and al-Halim. The first pairing is the striking one. Azim is immense — the attribute that could frighten. Halim is forbearing: the one who does not rush, who withholds punishment though able. Placing them together answers the fear that raw power provokes. The One in whose hands the situation lies is not only overwhelming; He is slow to strike.
Three Lords, widening. Then Lord of the Mighty Throne; then Lord of the heavens and the earth and the Noble Throne. The sentence expands outward from the throne to the created realms and back to the throne again, and the effect is spatial: the distress that filled a person's whole field of view is placed inside something much larger without ever being mentioned.
A common mix-up. This is not the supplication of Yunus said from inside the whale — la ilaha illa anta subhanaka inni kuntu min az-zalimin — which is also reached for in distress and is a different sentence with a different shape. Nor is it the supplication of Ayyub. All three share the habit of not stating a demand.