Rasulullah (Sallallaho Alaihi Wassallam) is reported to have said, “A person neglecting his Salaah (even though he makes it up later) shall remain in Jahannam for a period of one huqb. A Huqb is equal to eighty years of three hundred and sixty days each, and a day in Akhirah shall equal one thousand years of this world.” Huqb literally means a very long time; in most Ahadith it is explained as being eighty years as given above.
Abu al-Layth al-Samarqandi is responsible for the Hadith in which Rasulullah (Sallallaho Alaihi Wassallam) is reported to have said, “The name of a person who neglects even a single obligatory Salaah intentionally is written on the gate of Jahannam, which he must enter.”
Ibn Abbas (Radiallaho Anho) narrates that once Rasulullah (Sallallaho Alaihi Wassallam) said, “Ask Allah (Subhanahu wa Taala) to cause not anyone of us to be an unfortunate penniless.” He then said: “Do you know who is an unfortunate penniless?” At the request of the Sahabah he explained to them, saying, “An unfortunate penniless is he who neglects his Salaah. In Islam there is nothing for him.” In another Hadith it is said, “Allah (Subhanahu wa Taala) will not care a bit for the person who has been neglecting Salaah intentionally and for him shall be an awful punishment.
Conversely, deliberately missing prayers is an enormity, an action that is both punishable by a legal penalty in this world, and divine punishment in the Hereafter.
The Prophet, peace be upon him, said, “The agreement that is between us and them is the prayer: whoever leaves it has disbelieved.” [Reliance, p4.2]
In another hadith, it is narrated on the authority of Abu Zubair that he heard Jabir b. ‘Abdullah saying, ‘I heard the Messenger of Allah (may peace and blessings be upon him) observing this,’ “Between man and polytheism and unbelief is the abandonment of salat.” [Muslim]