Assalam O Alaikum
In case some one thinks that good deeds only can lead us to success in the World and hereafter, and following a religion (Islam) is not necessary please do read this:
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When his Lord said to him, Be a Muslim, he said: I submit myself to the Lord of the worlds.
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And the same did Ibrahim enjoin on his sons and (so did) Yaqoub. O my sons! surely Allah has chosen for you (this) faith, therefore die not unless you are Muslims.
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Surely the (true) religion with Allah is Islam, and those to whom the Book had been given did not show opposition but after knowledge had come to them, out of envy among themselves; and whoever disbelieves in the communications of Allah then surely Allah is quick in reckoning.
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But if they dispute with you, say: I have submitted myself entirely to Allah and (so) every one who follows me; and say to those who have been given the Book and the unlearned people: Do you submit yourselves? So if they submit then indeed they follow the right way; and if they turn back, then upon you is only the delivery of the message and Allah sees the servants.
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Surely (as for) those who disbelieve in the communications of Allah and slay the prophets unjustly and slay those among men who enjoin justice, announce to them a painful chastisement.
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Those are they whose works shall become null in this world as well as the hereafter, and they shall have no helpers.
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And whoever desires a religion other than Islam, it shall not be accepted from him, and in the hereafter he shall be one of the losers.
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O you who believe! be careful of (your duty to) Allah with the care which is due to Him, and do not die unless you are Muslims.
Sahih Bukhari - Volume 9, Book 92, Number 384:
Narrated Abu Huraira:
Allah’s Apostle said, “All my followers will enter Paradise except those who refuse.” They said, “O Allah’s Apostle! Who will refuse?” He said, “Whoever obeys me will enter Paradise, and whoever disobeys me is the one who refuses (to enter it).”
Sahih Bukhari - Volume 2, Book 23, Number 456:
Narrated Anas bin Malik:
Allah’s Apostle (PBUH) said, “When (Allah’s) slave is put in his grave and his companions return and he even hears their footsteps, two angels come to him and make him sit and ask, ‘What did you use to say about this man (i.e. Muhammad)?’ The faithful Believer will say, ‘I testify that he is Allah’s slave and His Apostle.’ Then they will say to him, ‘Look at your place in the Hell Fire; Allah has given you a place in Paradise instead of it.’ So he will see both his places.” (Qatada said, “We were informed that his grave would be made spacious.” Then Qatada went back to the narration of Anas who said a hypocrite or a non-believer will be asked, “What did you use to say about this man.” He will reply, “I do not know; but I used to say what the people used to say.” So they will say to him, “Neither did you know nor did you take the guidance (by reciting the Quran).” Then he will be hit with iron hammers once, that he will send such a cry as everything near to him will hear, except Jinns and human beings.
Sahih Bukhari - Volume 1, Book 2, Number 24:
Narrated Ibn 'Umar:
Allah’s Apostle said: “I have been ordered (by Allah) to fight against the people until they testify that none has the right to be worshipped but Allah and that Muhammad is Allah’s Apostle, and offer the prayers perfectly and give the obligatory charity, so if they perform a that, then they save their lives an property from me except for Islamic laws and then their reckoning (accounts) will be done by Allah.”
Assalam O Alaikum