The Essence
Al-Hayy is the Ever-Living, whose life is perfect, complete, and eternal. He has no beginning and no end, and He does not experience sleep, fatigue, or death.
In the Quran
اللَّهُ لَا إِلَهَ إِلَّا هُوَ الْحَيُّ الْقَيُّومُ
"Allah - there is no deity except Him, the Ever-Living (Al-Hayy), the Sustainer of [all] existence. (Surah Al-Baqarah 2:255)"
In Your Duas
يَا حَيُّ يَا قَيُّومُ بِرَحْمَتِكَ أَسْتَغِيثُ
"O Ever-Living (Hayy), O Sustainer (Qayyum), by Your mercy I seek assistance."
— Sunan at-Tirmidhi 3524