Isha is the fifth and last of the obligatory daily salah, prayed after the red and white twilight has left the sky and the night has fully set in. Its time extends longest of the five, through the first third or half of the night in the recommended reckoning, and by concession until the true dawn that begins the next day's Fajr. Its obligatory core is four rak'ah, the first two recited aloud and the last two silently, usually framed by sunnah cycles and completed, in the widely followed practice, by the odd-numbered witr prayer that seals the day's worship.
As the prayer that closes the daily round, Isha carries associations of completion and of watchfulness. A well-known saying pairs it with Fajr as the two prayers heaviest on the hypocrite and richest in reward for those who keep them in congregation, since both fall when it would be easiest to stay home.
The Prophet is reported to have discouraged calling the prayer by its old Arabian name, al-atama, associated with the time bedouin herders milked their camels, insisting instead on Isha, night, precisely to detach the obligation from a pastoral routine and root it in the specifically religious rhythm of the day; classical hadith collections preserve this correction as an explicit instance of Islamic practice reshaping pre-Islamic Arabian custom rather than simply inheriting it.