Assalmoelaikoem warahmatullahi wabaraktuh dear brothers and sisters,
You have to unite and understand the points of each other.
My brother mabsoot is following the opinion of the scholars who say: " The one who don't pray because of lazyness is a muslim " If i am wrong dear brother mabsoot correct me please.
And sister Samiha does the opposite. She follows the opinion of the scholars who say: " The one who does not pray because of lazyness or denying Salah ( prayer) is a non-muslim ( a kafir)"
So there are difference in opinion which are based on the interpretation of various verses ( Ayaat) and ahadieth.
This is also what our sister Samiha has mentioned:"there are differences of opinion based on whether the person denys Salah or doen't do it out of lazyness"
But she gave only the evidences which are given by those scholars who Samiha Follows . And because she mentioned that there are difference in opinion , I will mention the ahadieth and Quranic verses which are used by the scholars of the first opinion. And the interpretation of the ahadieth and Quranic verses which samiha has mentioned.
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"Then, there has succeeded them a posterity who have given up As-Salât (the prayers) [i.e. made their Salât (prayers) to be lost, either by not offering them or by not offering them perfectly or by not offering them in their proper fixed times, etc.] and have followed lusts. So they will be thrown in Hell". [19:59]
Not praying because of lazyness is a major sin following the first opinion. The people who don't pray because of lazyness they can be thrown in Hell. But this does not mean they are not muslim, but Allah can forgive them. It's up to Allah to throw them in Hell and when the Hell has cleaned them from the sins they can be lifted from the hell and put in paradise.
Allah said:
إِنَّ اللّهَ لاَ يَغْفِرُ أَن يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَلِكَ لِمَن يَشَاء وَمَن يُشْرِكْ بِاللّهِ فَقَدِ افْتَرَى إِثْمًا عَظِيمًاِ
إِنَّ اللّهَ لاَ يَغْفِرُ أَن يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَلِكَ لِمَن يَشَاء وَمَن يُشْرِكْ بِاللّهِ فَقَدْ ضَلَّ ضَلاَلاً بَعِيدًاِ
{God forgiveth not (the sin of) joining other gods with Him; but He forgiveth whom He pleaseth other sins than this; one who joins other gods with God, Hath strayed far, far away (from the right).}[4: 116]. This is a translation of the second verse i gave in arabic.
hadieth : Narrated 'Utban bin Malik Al-Ansari: who was one of the men of the tribe of Bani Salim: Allah's Apostle came to me and said, "If anybody comes on the Day of Resurrection who has said: La ilaha illal-lah, sincerely, with the intention to win Allah's Pleasure, Allah will make the Hell-Fire forbidden for him."
And do you know the hadieth of the one who is a muslim and will enter Hell. When he is cleaned from the sins he will be lifted from it and will enter paradise
Narrated 'Ubada:
The Prophet said, "If anyone testifies that None has the right to be worshipped but Allah Alone Who has no partners, and that Muhammad is His Slave and His Apostle, and that Jesus is Allah's Slave and His Apostle and His Word which He bestowed on Mary and a Spirit created by Him, and that Paradise is true, and Hell is true, Allah will admit him into Paradise with the deeds which he had done even if those deeds were few." (Junada, the sub-narrator said, " 'Ubada added, 'Such a person can enter Paradise through any of its eight gates he likes.") ( sahih el Bukhari)
Insha Allah if i have time i will go further on this. But i have to make clear that i follow the first opinion like our brother mabsoot.
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The one who follows the first opinion he will give salaam to the one who don't pray because of lazyness. He is a muslim regarding his opinion. And the one who follows the second opinion he will not give the salaam, because he don't sees him as a muslim.
This is only a sumary about the difference of opinion based upon difference in interpretation of the ahadieth and Quraan verses.
And dear sister Ruqhya you said: " The Muslim whom is a hypocrite will be in the lowest part of Hell. "
Allah says : "Verily the hypocrites will be in the lowest depths [grade] of the Fire"(4:145
But this are not muslim so be carefull.