Abandoning the Prayer is Not Apostasy
30-5-2018 | IslamWeb
Question:
salam. what is this website's view on a Muslim who doesn't pray (is he kafir or not)? and what is its evidence behind the view?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
This issue is a matter about which the scholars have greatly differed in opinion. However, you should know that the extent that is agreed upon among the Muslims is what Ibn Al-Qayyim 
said at the beginning of chapter As-Salah (the Prayer) that whoever abandons one single prayer deliberately until its prescribed time is over, he is worse than the adulterer (or fornicator), the thief, the consumer of intoxicants, and the killer of a soul, and that he subjects himself to an evil end of his life, we seek refuge of Allah in that. He is also vulnerable to the immediate punishment of Allah in this worldly life as well as the punishment in the Hereafter. This makes every sane person extremely fearful of committing this heinous act [abandoning the prayer once].
As regards whether or not he goes out of the fold of Islam, then the view that we adopt here in Islamweb is the view of the majority of the scholars, that he does not go out of the fold of Islam by abandoning the prayer as long as he does not deny its obligation, although he is the most evil of dissolute people and the most vulnerable of them to the serious danger.
The evidence for this is that Allah Says (what means): {Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills.} [Quran 4:48]
‘Ubaadah ibn As-Saamit 
narrated that the Prophet said: “Allah, the Exalted, has made five prayers obligatory. If anyone properly performs ablution for them, offers them at their exact time, and observes perfectly bowing and submissiveness in them, then Allah guarantees that He will pardon him. However, the one who does not do so, then there is no guarantee for him on the part of Allah; He may pardon him if He wills, or punish him if He wills.” [Abu Daawood]
The fact that such a person is included under the Will of Allah is evidence that he is among the disobedient people and not out of the fold of Islam.
This issue is very long to debate so you may read more about it in the large books of Fiqh.
Allah knows best.