Isha stands at the threshold of the voluntary night worship that Islamic devotion prizes highly. The recommended witr prayer is prayed after it, and the deeper night beyond Isha is the field of tahajjud, the vigil of those who rise to pray while others sleep, and, in Ramadan, of the tarawih prayers performed in congregation after Isha, in which long portions of the Qur'an are recited across the nights of the month.
The schools discuss whether delaying Isha into the later night is preferable to praying it early; the reported practice of the Prophet supports a moderate delay where it does not burden the congregation. Twelver Shia practice commonly joins Isha to the preceding Maghrib, praying both after sunset, so that the night obligation is discharged early and the remaining hours left free for voluntary devotion.
Quranic exegetes have long noted that Surah al-Muzzammil originally impressed night vigil on the Prophet and the earliest believers as a near-continuous discipline, before its concluding verse (73:20) explicitly eased the requirement in recognition that believers have work, travel, and illness to contend with, a textual softening early commentators read as the model for how tahajjud later settled into a voluntary rather than obligatory practice even as its spiritual prestige remained exceptionally high.