“Whenever a matter would distress him, the Prophet (ﷺ) would say: ‘O Living, O Self-Sustaining Sustainer! In Your Mercy do I seek relief (Yā Ḥayyu yā Qayyūm, bi-raḥmatika astaghīth).’” And with this chain, that he said: “The Messenger of Allah (ﷺ) said: ‘Be constant with: “O Possessor of Majesty and Honor (Yā Dhal-Jalāli wal-Ikrām).’”
Jami` at-Tirmidhi Book 48, Hadith 155