When is a person regarded as neglecting prayer, and what is the ruling on him?
Question

Persons who are “not praying at all” are considered non-Muslims. Are those praying only during Eid’l Fitr, Eid’l Adha , and sometimes every Friday and / or sometimes during one of the five daily prayers fall in the term “not praying at all” hence they are considered as non-Muslims? How is “not praying at all” construed or interpreted?.
Praise be to Allah.Firstly: 
The one who neglects prayer is one who does not pray at all, and he is a kaafir regardless of whether that is due to laziness or denying that the prayer is obligatory, according to the more correct of the two scholarly opinions. This is based on a great deal of evidence, some of which has been mentioned in the answer to question no. 5208. 
Secondly: 
If a person is not omitting all prayers, rather he prays sometimes and does not pray sometimes, then those who say that the one who does not pray is a kaafir differed in this case. Some of them said that he is a kaafir if he deliberately does not offer an obligatory prayer until the time for it is over on one occasion; so the one who deliberately does not pray Fajr until the sun has risen becomes a kaafir, and the one who deliberately does not pray Zuhr until the sun sets becomes a kaafir, because Zuhr may be joined with ‘Asr, so the time for both is the same, when one has an excuse; and the same applies to Maghrib and ‘Isha’, the one who deliberately does not pray Maghrib until the time for ‘Isha’ ends becomes a kaafir. 
Some of them say that he does not become a kaafir unless he fails to pray permanently. 
Imam Muhammad ibn Nasr al-Marwazi (may Allah have mercy on him) said: I heard Ishaaq say: It was narrated in a saheeh report from the Messenger of Allah (peace and blessings of Allah be upon him) that the one who does not pray is a kaafir. This was also the view of the scholars from the time of the Prophet (peace and blessings of Allah be upon him) until the present, that the one who deliberately does not pray with no excuse, until the time for the prayer ends, becomes a kaafir. Until the time ends means delaying Zuhr until sunset or delaying Maghrib until dawn comes. 
The end of the time for prayer is described thus because the Prophet (peace and blessings of Allah be upon him) joined two prayers in ‘Arafah and Muzdalifah, and when travelling, so he prayed one of them at the time of the other. When the Prophet (peace and blessings of Allah be upon him) did the first prayer at the time of the second in one case, or the second at the time of the first in another case, the time for both became the same in cases where there is an excuse. Hence if a menstruating woman becomes pure before sunset, she is enjoined to pray both Zuhr and ‘Asr, and if she becomes pure at the end of the night she is enjoined to pray Maghrib and ‘Isha’. End quote from Ta’zeem Qadr al-Salaah (2/929). 
Ibn Hazm (may Allah be pleased with him) said: We have narrated from ‘Umar ibn al-Khattaab (may Allah be pleased with him), Mu’aadh ibn Jabal, Ibn Mas’ood, a number of the Sahaabah (may Allah be pleased with them), and from Ibn al-Mubaarak, Ahmad ibn Hanbal, Ishaaq ibn Raahawayh (may Allah have mercy on them)and from other Sahaabah (may Allah be pleased with them),a total of seventeen, that the one who deliberately and knowingly does not offer an obligatory prayer until the time for it has ended becomes a kaafir and apostate. This is the view of ‘Abd-Allah ibn al-Maajishoon, the companion of Maalik, and of ‘Abd al-Malik ibn Habeeb al-Andaloosi and others. End quote from al-Fasl fi’l-Milal wa’l-Ahwa’ wa’l-Nihal (3/128). 
And he (may Allah have mercy on him) said: It was narrated from ‘Umar, ‘Abd al-Rahmaan ibn ‘Awf, Mu’aadh ibn Jabal, Abu Hurayrah and others among the Sahaabah (may Allah be pleased with them) that the one who deliberately does not offer an obligatory prayer once, until the time for it has ended, is a kaafir and an apostate. End quote from al-Muhalla (2/15).
Fatwas based on this view have been issued by the Standing Committee, under the leadership of Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him). Fataawa al-Lajnah al-Daa’imah (6/40, 50). 
Among those who have issued fatwas stating that the one who does not pray is not a kaafir unless he stops praying altogether or permanently is Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him). He was asked about a person who prays sometimes and does not pray at other times. Is he a kaafir? 
He replied: It seems to me that he is not a kaafir unless he does not pray at all. As for one who prays sometimes, he is not a kaafir because the Messenger (peace and blessings of Allah be upon him) said: “Between a man and kufr and shirk there stands his giving up prayer.” He did not say “giving up a prayer” (tarku salaatin) rather he said “giving up [the] prayer” (tark al-salaah). This implies not praying altogether. Similarly he said: “The covenant that distinguishes between us and them is prayer; whoever does not pray is a kaafir.” Based on that we say: The one who prays sometimes and does not pray sometimes is not a kaafir. End quote from Majmoo’ Fataawa Ibn ‘Uthaymeen (12/55). 
But he was asked about one who only prays Jumu’ah (Friday prayer) and he replied: He only prays Jumu’ah? Why does he only pray Jumu’ah? 
The questioner said: That is his habit. 
He replied: If it is his habit then he does not believe that his prayer is an act of worship. So he prays Jumu’ah out of habit and he gets dressed and makes himself look good and puts on perfume and goes. Even if I do not think that anyone is a kaafir except the one who does not pray at all, I would still have doubts about this man’s Islam, because he is taking Jumu’ah prayer as a special occasion only, and he dresses up and goes to meet people, when he is wearing perfume and dressed up. I doubt whether he is still Muslim. According to the opinion of our Shaykh ‘Abd al-‘Azeez he is a kaafir. End quote from Liqa’ al-Baab il-Maftooh. 
And Allah knows best.