Silsilat al-Ahadith al-Sahihah

A companion from the tribe of Juhainah narrates: I asked the Messenger of Allah (peace and blessings be upon him): When should I perform the ‘Isha prayer? The Prophet (peace and blessings be upon him) said: “Perform the ‘Isha prayer when the night fills the belly of every valley (i.e., when the night has completely settled over every valley).”